Managing Directory-Tree Operations in File Storage

ABSTRACT

An illustrative data storage system establishes path sets that represent relationships between service layer entities and storage layer entities associated with service layer entities. The data storage system coordinates, based on the path sets and on operations applied to one or more of the service layer entities, implementation of the operations on the storage layer entities. The path sets may be used to support implementation of snapshots, space accounting, and/or other operations of the data storage system.

RELATED APPLICATIONS

The present application is a continuation-in-part application of U.S.patent application Ser. No. 16/834,762, entitled “Unified Storage onBlock Containers” and filed on Mar. 30, 2020. The present applicationalso claims priority to U.S. Provisional Patent Application No.63/036,955, entitled “Managing Snapshots of Directories in File Systems”and filed on Jun. 9, 2020, and to U.S. Provisional Patent ApplicationNo. 63/077,259, entitled “Space Accounting in a Storage System” andfiled Sep. 11, 2020. These applications are expressly incorporated byreference herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments and are a partof the specification. The illustrated embodiments are merely examplesand do not limit the scope of the disclosure. Throughout the drawings,identical or similar reference numbers designate identical or similarelements.

FIG. 1A illustrates a first example system for data storage inaccordance with some implementations.

FIG. 1B illustrates a second example system for data storage inaccordance with some implementations.

FIG. 1C illustrates a third example system for data storage inaccordance with some implementations.

FIG. 1D illustrates a fourth example system for data storage inaccordance with some implementations.

FIG. 2A is a perspective view of a storage cluster with multiple storagenodes and internal storage coupled to each storage node to providenetwork attached storage, in accordance with some embodiments.

FIG. 2B is a block diagram showing an interconnect switch couplingmultiple storage nodes in accordance with some embodiments.

FIG. 2C is a multiple level block diagram, showing contents of a storagenode and contents of one of the non-volatile solid state storage unitsin accordance with some embodiments.

FIG. 2D shows a storage server environment, which uses embodiments ofthe storage nodes and storage units of some previous FIG.s in accordancewith some embodiments.

FIG. 2E is a blade hardware block diagram, showing a control plane,compute and storage planes, and authorities interacting with underlyingphysical resources, in accordance with some embodiments.

FIG. 2F depicts elasticity software layers in blades of a storagecluster, in accordance with some embodiments.

FIG. 2G depicts authorities and storage resources in blades of a storagecluster, in accordance with some embodiments.

FIG. 3A sets forth a diagram of a storage system that is coupled fordata communications with a cloud services provider in accordance withsome embodiments of the present disclosure.

FIG. 3B sets forth a diagram of a storage system in accordance with someembodiments of the present disclosure.

FIG. 3C sets forth an example of a cloud-based storage system inaccordance with some embodiments of the present disclosure.

FIG. 3D illustrates an example of a computing device that may bespecifically configured to perform one or more of the processesdescribed herein in accordance with some embodiments of the presentdisclosure.

FIGS. 4A-4B illustrate an example of a data storage system that includesa block container system and a container utilization system inaccordance with some embodiments of the present disclosure.

FIG. 5 illustrates an example of a data structure resource used torepresent a data instance in accordance with some embodiments.

FIGS. 6A-B illustrate examples of data storage service systemsconfigured to interface with a container utilization system inaccordance with some embodiments of the present disclosure.

FIGS. 7-11 illustrate example methods of a data storage system inaccordance with some embodiments of the present disclosure.

FIG. 12 illustrates an example of a data storage system in accordancewith some embodiments of the present disclosure.

FIGS. 13A-13C illustrate examples of path sets in accordance with someembodiments of the present disclosure.

FIG. 14 illustrates an example of a data storage system in accordancewith some embodiments of the present disclosure.

FIG. 15 illustrates an example of path sets in accordance with someembodiments of the present disclosure.

FIG. 16 illustrates an example of versioned path sets associated withsnapshots of a directory in accordance with some embodiments of thepresent disclosure.

FIG. 17 illustrates an example of establishment and use of path sets tocoordinate implementation of snapshots on block objects in accordancewith some embodiments of the present disclosure.

FIG. 18 illustrates an example of path sets in accordance with someembodiments of the present disclosure.

FIG. 19 illustrates an example of establishment and use of path sets tocoordinate implementation of snapshots on block objects in accordancewith some embodiments of the present disclosure.

FIGS. 20-22 illustrate example methods of snapshot management for astorage system in accordance with some embodiments of the presentdisclosure.

DESCRIPTION OF EMBODIMENTS

Example methods, apparatus, and products for data storage in accordancewith embodiments of the present disclosure are described with referenceto the accompanying drawings, beginning with FIG. 1A. FIG. 1Aillustrates an example system for data storage, in accordance with someimplementations. System 100 (also referred to as “storage system”herein) includes numerous elements for purposes of illustration ratherthan limitation. It may be noted that system 100 may include the same,more, or fewer elements configured in the same or different manner inother implementations.

System 100 includes a number of computing devices 164A-B. Computingdevices (also referred to as “client devices” herein) may be embodied,for example, a server in a data center, a workstation, a personalcomputer, a notebook, or the like. Computing devices 164A-B may becoupled for data communications to one or more storage arrays 102A-Bthrough a storage area network (‘SAN’) 158 or a local area network(‘LAN’) 160.

The SAN 158 may be implemented with a variety of data communicationsfabrics, devices, and protocols. For example, the fabrics for SAN 158may include Fibre Channel, Ethernet, Infiniband, Serial Attached SmallComputer System Interface (‘SAS’), or the like. Data communicationsprotocols for use with SAN 158 may include Advanced TechnologyAttachment (‘ATA’), Fibre Channel Protocol, Small Computer SystemInterface (‘SCSI’), Internet Small Computer System Interface (‘iSCSI’),HyperSCSI, Non-Volatile Memory Express (‘NVMe’) over Fabrics, or thelike. It may be noted that SAN 158 is provided for illustration, ratherthan limitation. Other data communication couplings may be implementedbetween computing devices 164A-B and storage arrays 102A-B.

The LAN 160 may also be implemented with a variety of fabrics, devices,and protocols. For example, the fabrics for LAN 160 may include Ethernet(802.3), wireless (802.11), or the like. Data communication protocolsfor use in LAN 160 may include Transmission Control Protocol (‘TCP’),User Datagram Protocol (‘UDP’), Internet Protocol (‘IP’), HyperTextTransfer Protocol (‘HTTP’), Wireless Access Protocol (‘WAP’), HandheldDevice Transport Protocol (‘HDTP’), Session Initiation Protocol (‘SIP’),Real Time Protocol (‘RTP’), or the like.

Storage arrays 102A-B may provide persistent data storage for thecomputing devices 164A-B. Storage array 102A may be contained in achassis (not shown), and storage array 102B may be contained in anotherchassis (not shown), in implementations. Storage array 102A and 102B mayinclude one or more storage array controllers 110A-D (also referred toas “controller” herein). A storage array controller 110A-D may beembodied as a module of automated computing machinery comprisingcomputer hardware, computer software, or a combination of computerhardware and software. In some implementations, the storage arraycontrollers 110A-D may be configured to carry out various storage tasks.Storage tasks may include writing data received from the computingdevices 164A-B to storage array 102A-B, erasing data from storage array102A-B, retrieving data from storage array 102A-B and providing data tocomputing devices 164A-B, monitoring and reporting of disk utilizationand performance, performing redundancy operations, such as RedundantArray of Independent Drives (‘RAID’) or RAID-like data redundancyoperations, compressing data, encrypting data, and so forth.

Storage array controller 110A-D may be implemented in a variety of ways,including as a Field Programmable Gate Array (‘FPGA’), a ProgrammableLogic Chip (‘PLC’), an Application Specific Integrated Circuit (‘ASIC’),System-on-Chip (‘SOC’), or any computing device that includes discretecomponents such as a processing device, central processing unit,computer memory, or various adapters. Storage array controller 110A-Dmay include, for example, a data communications adapter configured tosupport communications via the SAN 158 or LAN 160. In someimplementations, storage array controller 110A-D may be independentlycoupled to the LAN 160. In implementations, storage array controller110A-D may include an I/O controller or the like that couples thestorage array controller 110A-D for data communications, through amidplane (not shown), to a persistent storage resource 170A-B (alsoreferred to as a “storage resource” herein). The persistent storageresource 170A-B main include any number of storage drives 171A-F (alsoreferred to as “storage devices” herein) and any number of non-volatileRandom Access Memory (‘NVRAM’) devices (not shown).

In some implementations, the NVRAM devices of a persistent storageresource 170A-B may be configured to receive, from the storage arraycontroller 110A-D, data to be stored in the storage drives 171A-F. Insome examples, the data may originate from computing devices 164A-B. Insome examples, writing data to the NVRAM device may be carried out morequickly than directly writing data to the storage drive 171A-F. Inimplementations, the storage array controller 110A-D may be configuredto utilize the NVRAM devices as a quickly accessible buffer for datadestined to be written to the storage drives 171A-F. Latency for writerequests using NVRAM devices as a buffer may be improved relative to asystem in which a storage array controller 110A-D writes data directlyto the storage drives 171A-F. In some implementations, the NVRAM devicesmay be implemented with computer memory in the form of high bandwidth,low latency RAM. The NVRAM device is referred to as “non-volatile”because the NVRAM device may receive or include a unique power sourcethat maintains the state of the RAM after main power loss to the NVRAMdevice. Such a power source may be a battery, one or more capacitors, orthe like. In response to a power loss, the NVRAM device may beconfigured to write the contents of the RAM to a persistent storage,such as the storage drives 171A-F.

In implementations, storage drive 171A-F may refer to any deviceconfigured to record data persistently, where “persistently” or“persistent” refers as to a device's ability to maintain recorded dataafter loss of power. In some implementations, storage drive 171A-F maycorrespond to non-disk storage media. For example, the storage drive171A-F may be one or more solid-state drives (‘SSDs’), flash memorybased storage, any type of solid-state non-volatile memory, or any othertype of non-mechanical storage device. In other implementations, storagedrive 171A-F may include mechanical or spinning hard disk, such ashard-disk drives (‘HDD’).

In some implementations, the storage array controllers 110A-D may beconfigured for offloading device management responsibilities fromstorage drive 171A-F in storage array 102A-B. For example, storage arraycontrollers 110A-D may manage control information that may describe thestate of one or more memory blocks in the storage drives 171A-F. Thecontrol information may indicate, for example, that a particular memoryblock has failed and should no longer be written to, that a particularmemory block contains boot code for a storage array controller 110A-D,the number of program-erase (‘P/E’) cycles that have been performed on aparticular memory block, the age of data stored in a particular memoryblock, the type of data that is stored in a particular memory block, andso forth. In some implementations, the control information may be storedwith an associated memory block as metadata. In other implementations,the control information for the storage drives 171A-F may be stored inone or more particular memory blocks of the storage drives 171A-F thatare selected by the storage array controller 110A-D. The selected memoryblocks may be tagged with an identifier indicating that the selectedmemory block contains control information. The identifier may beutilized by the storage array controllers 110A-D in conjunction withstorage drives 171A-F to quickly identify the memory blocks that containcontrol information. For example, the storage controllers 110A-D mayissue a command to locate memory blocks that contain controlinformation. It may be noted that control information may be so largethat parts of the control information may be stored in multiplelocations, that the control information may be stored in multiplelocations for purposes of redundancy, for example, or that the controlinformation may otherwise be distributed across multiple memory blocksin the storage drive 171A-F.

In implementations, storage array controllers 110A-D may offload devicemanagement responsibilities from storage drives 171A-F of storage array102A-B by retrieving, from the storage drives 171A-F, controlinformation describing the state of one or more memory blocks in thestorage drives 171A-F. Retrieving the control information from thestorage drives 171A-F may be carried out, for example, by the storagearray controller 110A-D querying the storage drives 171A-F for thelocation of control information for a particular storage drive 171A-F.The storage drives 171A-F may be configured to execute instructions thatenable the storage drive 171A-F to identify the location of the controlinformation. The instructions may be executed by a controller (notshown) associated with or otherwise located on the storage drive 171A-Fand may cause the storage drive 171A-F to scan a portion of each memoryblock to identify the memory blocks that store control information forthe storage drives 171A-F. The storage drives 171A-F may respond bysending a response message to the storage array controller 110A-D thatincludes the location of control information for the storage drive171A-F. Responsive to receiving the response message, storage arraycontrollers 110A-D may issue a request to read data stored at theaddress associated with the location of control information for thestorage drives 171A-F.

In other implementations, the storage array controllers 110A-D mayfurther offload device management responsibilities from storage drives171A-F by performing, in response to receiving the control information,a storage drive management operation. A storage drive managementoperation may include, for example, an operation that is typicallyperformed by the storage drive 171A-F (e.g., the controller (not shown)associated with a particular storage drive 171A-F). A storage drivemanagement operation may include, for example, ensuring that data is notwritten to failed memory blocks within the storage drive 171A-F,ensuring that data is written to memory blocks within the storage drive171A-F in such a way that adequate wear leveling is achieved, and soforth.

In implementations, storage array 102A-B may implement two or morestorage array controllers 110A-D. For example, storage array 102A mayinclude storage array controllers 110A and storage array controllers110B. At a given instance, a single storage array controller 110A-D(e.g., storage array controller 110A) of a storage system 100 may bedesignated with primary status (also referred to as “primary controller”herein), and other storage array controllers 110A-D (e.g., storage arraycontroller 110A) may be designated with secondary status (also referredto as “secondary controller” herein). The primary controller may haveparticular rights, such as permission to alter data in persistentstorage resource 170A-B (e.g., writing data to persistent storageresource 170A-B). At least some of the rights of the primary controllermay supersede the rights of the secondary controller. For instance, thesecondary controller may not have permission to alter data in persistentstorage resource 170A-B when the primary controller has the right. Thestatus of storage array controllers 110A-D may change. For example,storage array controller 110A may be designated with secondary status,and storage array controller 110B may be designated with primary status.

In some implementations, a primary controller, such as storage arraycontroller 110A, may serve as the primary controller for one or morestorage arrays 102A-B, and a second controller, such as storage arraycontroller 110B, may serve as the secondary controller for the one ormore storage arrays 102A-B. For example, storage array controller 110Amay be the primary controller for storage array 102A and storage array102B, and storage array controller 110B may be the secondary controllerfor storage array 102A and 102B. In some implementations, storage arraycontrollers 110C and 110D (also referred to as “storage processingmodules”) may neither have primary or secondary status. Storage arraycontrollers 110C and 110D, implemented as storage processing modules,may act as a communication interface between the primary and secondarycontrollers (e.g., storage array controllers 110A and 110B,respectively) and storage array 102B. For example, storage arraycontroller 110A of storage array 102A may send a write request, via SAN158, to storage array 102B. The write request may be received by bothstorage array controllers 110C and 110D of storage array 102B. Storagearray controllers 110C and 110D facilitate the communication, e.g., sendthe write request to the appropriate storage drive 171A-F. It may benoted that in some implementations storage processing modules may beused to increase the number of storage drives controlled by the primaryand secondary controllers.

In implementations, storage array controllers 110A-D are communicativelycoupled, via a midplane (not shown), to one or more storage drives171A-F and to one or more NVRAM devices (not shown) that are included aspart of a storage array 102A-B. The storage array controllers 110A-D maybe coupled to the midplane via one or more data communication links andthe midplane may be coupled to the storage drives 171A-F and the NVRAMdevices via one or more data communications links. The datacommunications links described herein are collectively illustrated bydata communications links 108A-D and may include a Peripheral ComponentInterconnect Express (‘PCIe’) bus, for example.

FIG. 1B illustrates an example system for data storage, in accordancewith some implementations. Storage array controller 101 illustrated inFIG. 1B may similar to the storage array controllers 110A-D describedwith respect to FIG. 1A. In one example, storage array controller 101may be similar to storage array controller 110A or storage arraycontroller 110B. Storage array controller 101 includes numerous elementsfor purposes of illustration rather than limitation. It may be notedthat storage array controller 101 may include the same, more, or fewerelements configured in the same or different manner in otherimplementations. It may be noted that elements of FIG. 1A may beincluded below to help illustrate features of storage array controller101.

Storage array controller 101 may include one or more processing devices104 and random access memory (‘RAM’) 111. Processing device 104 (orcontroller 101) represents one or more general-purpose processingdevices such as a microprocessor, central processing unit, or the like.More particularly, the processing device 104 (or controller 101) may bea complex instruction set computing (‘CISC’) microprocessor, reducedinstruction set computing (‘RISC’) microprocessor, very long instructionword (‘VLIW’) microprocessor, or a processor implementing otherinstruction sets or processors implementing a combination of instructionsets. The processing device 104 (or controller 101) may also be one ormore special-purpose processing devices such as an ASIC, an FPGA, adigital signal processor (‘DSP’), network processor, or the like.

The processing device 104 may be connected to the RAM 111 via a datacommunications link 106, which may be embodied as a high speed memorybus such as a Double-Data Rate 4 (‘DDR4’) bus. Stored in RAM 111 is anoperating system 112. In some implementations, instructions 113 arestored in RAM 111. Instructions 113 may include computer programinstructions for performing operations in in a direct-mapped flashstorage system. In one embodiment, a direct-mapped flash storage systemis one that that addresses data blocks within flash drives directly andwithout an address translation performed by the storage controllers ofthe flash drives.

In implementations, storage array controller 101 includes one or morehost bus adapters 103A-C that are coupled to the processing device 104via a data communications link 105A-C. In implementations, host busadapters 103A-C may be computer hardware that connects a host system(e.g., the storage array controller) to other network and storagearrays. In some examples, host bus adapters 103A-C may be a FibreChannel adapter that enables the storage array controller 101 to connectto a SAN, an Ethernet adapter that enables the storage array controller101 to connect to a LAN, or the like. Host bus adapters 103A-C may becoupled to the processing device 104 via a data communications link105A-C such as, for example, a PCIe bus.

In implementations, storage array controller 101 may include a host busadapter 114 that is coupled to an expander 115. The expander 115 may beused to attach a host system to a larger number of storage drives. Theexpander 115 may, for example, be a SAS expander utilized to enable thehost bus adapter 114 to attach to storage drives in an implementationwhere the host bus adapter 114 is embodied as a SAS controller.

In implementations, storage array controller 101 may include a switch116 coupled to the processing device 104 via a data communications link109. The switch 116 may be a computer hardware device that can createmultiple endpoints out of a single endpoint, thereby enabling multipledevices to share a single endpoint. The switch 116 may, for example, bea PCIe switch that is coupled to a PCIe bus (e.g., data communicationslink 109) and presents multiple PCIe connection points to the midplane.

In implementations, storage array controller 101 includes a datacommunications link 107 for coupling the storage array controller 101 toother storage array controllers. In some examples, data communicationslink 107 may be a QuickPath Interconnect (QPI) interconnect.

A traditional storage system that uses traditional flash drives mayimplement a process across the flash drives that are part of thetraditional storage system. For example, a higher level process of thestorage system may initiate and control a process across the flashdrives. However, a flash drive of the traditional storage system mayinclude its own storage controller that also performs the process. Thus,for the traditional storage system, a higher level process (e.g.,initiated by the storage system) and a lower level process (e.g.,initiated by a storage controller of the storage system) may both beperformed.

To resolve various deficiencies of a traditional storage system,operations may be performed by higher level processes and not by thelower level processes. For example, the flash storage system may includeflash drives that do not include storage controllers that provide theprocess. Thus, the operating system of the flash storage system itselfmay initiate and control the process. This may be accomplished by adirect-mapped flash storage system that addresses data blocks within theflash drives directly and without an address translation performed bythe storage controllers of the flash drives.

The operating system of the flash storage system may identify andmaintain a list of allocation units across multiple flash drives of theflash storage system. The allocation units may be entire erase blocks ormultiple erase blocks. The operating system may maintain a map oraddress range that directly maps addresses to erase blocks of the flashdrives of the flash storage system.

Direct mapping to the erase blocks of the flash drives may be used torewrite data and erase data. For example, the operations may beperformed on one or more allocation units that include a first data anda second data where the first data is to be retained and the second datais no longer being used by the flash storage system. The operatingsystem may initiate the process to write the first data to new locationswithin other allocation units and erasing the second data and markingthe allocation units as being available for use for subsequent data.Thus, the process may only be performed by the higher level operatingsystem of the flash storage system without an additional lower levelprocess being performed by controllers of the flash drives.

Advantages of the process being performed only by the operating systemof the flash storage system include increased reliability of the flashdrives of the flash storage system as unnecessary or redundant writeoperations are not being performed during the process. One possiblepoint of novelty here is the concept of initiating and controlling theprocess at the operating system of the flash storage system. Inaddition, the process can be controlled by the operating system acrossmultiple flash drives. This is contrast to the process being performedby a storage controller of a flash drive.

A storage system can consist of two storage array controllers that sharea set of drives for failover purposes, or it could consist of a singlestorage array controller that provides a storage service that utilizesmultiple drives, or it could consist of a distributed network of storagearray controllers each with some number of drives or some amount ofFlash storage where the storage array controllers in the networkcollaborate to provide a complete storage service and collaborate onvarious aspects of a storage service including storage allocation andgarbage collection.

FIG. 1C illustrates a third example system 117 for data storage inaccordance with some implementations. System 117 (also referred to as“storage system” herein) includes numerous elements for purposes ofillustration rather than limitation. It may be noted that system 117 mayinclude the same, more, or fewer elements configured in the same ordifferent manner in other implementations.

In one embodiment, system 117 includes a dual Peripheral ComponentInterconnect (‘PCI’) flash storage device 118 with separatelyaddressable fast write storage. System 117 may include a storagecontroller 119. In one embodiment, storage controller 119A-D may be aCPU, ASIC, FPGA, or any other circuitry that may implement controlstructures necessary according to the present disclosure. In oneembodiment, system 117 includes flash memory devices (e.g., includingflash memory devices 120 a-n), operatively coupled to various channelsof the storage device controller 119. Flash memory devices 120 a-n, maybe presented to the controller 119A-D as an addressable collection ofFlash pages, erase blocks, and/or control elements sufficient to allowthe storage device controller 119A-D to program and retrieve variousaspects of the Flash. In one embodiment, storage device controller119A-D may perform operations on flash memory devices 120 a-n includingstoring and retrieving data content of pages, arranging and erasing anyblocks, tracking statistics related to the use and reuse of Flash memorypages, erase blocks, and cells, tracking and predicting error codes andfaults within the Flash memory, controlling voltage levels associatedwith programming and retrieving contents of Flash cells, etc.

In one embodiment, system 117 may include RAM 121 to store separatelyaddressable fast-write data. In one embodiment, RAM 121 may be one ormore separate discrete devices. In another embodiment, RAM 121 may beintegrated into storage device controller 119A-D or multiple storagedevice controllers. The RAM 121 may be utilized for other purposes aswell, such as temporary program memory for a processing device (e.g., aCPU) in the storage device controller 119.

In one embodiment, system 117 may include a stored energy device 122,such as a rechargeable battery or a capacitor. Stored energy device 122may store energy sufficient to power the storage device controller 119,some amount of the RAM (e.g., RAM 121), and some amount of Flash memory(e.g., Flash memory 120 a-120 n) for sufficient time to write thecontents of RAM to Flash memory. In one embodiment, storage devicecontroller 119A-D may write the contents of RAM to Flash Memory if thestorage device controller detects loss of external power.

In one embodiment, system 117 includes two data communications links 123a, 123 b. In one embodiment, data communications links 123 a, 123 b maybe PCI interfaces. In another embodiment, data communications links 123a, 123 b may be based on other communications standards (e.g.,HyperTransport, InfiniBand, etc.). Data communications links 123 a, 123b may be based on non-volatile memory express (‘NVMe’) or NVMe overfabrics (‘NVMf’) specifications that allow external connection to thestorage device controller 119A-D from other components in the storagesystem 117. It should be noted that data communications links may beinterchangeably referred to herein as PCI buses for convenience.

System 117 may also include an external power source (not shown), whichmay be provided over one or both data communications links 123 a, 123 b,or which may be provided separately. An alternative embodiment includesa separate Flash memory (not shown) dedicated for use in storing thecontent of RAM 121. The storage device controller 119A-D may present alogical device over a PCI bus which may include an addressablefast-write logical device, or a distinct part of the logical addressspace of the storage device 118, which may be presented as PCI memory oras persistent storage. In one embodiment, operations to store into thedevice are directed into the RAM 121. On power failure, the storagedevice controller 119A-D may write stored content associated with theaddressable fast-write logical storage to Flash memory (e.g., Flashmemory 120 a-n) for long-term persistent storage.

In one embodiment, the logical device may include some presentation ofsome or all of the content of the Flash memory devices 120 a-n, wherethat presentation allows a storage system including a storage device 118(e.g., storage system 117) to directly address Flash memory pages anddirectly reprogram erase blocks from storage system components that areexternal to the storage device through the PCI bus. The presentation mayalso allow one or more of the external components to control andretrieve other aspects of the Flash memory including some or all of:tracking statistics related to use and reuse of Flash memory pages,erase blocks, and cells across all the Flash memory devices; trackingand predicting error codes and faults within and across the Flash memorydevices; controlling voltage levels associated with programming andretrieving contents of Flash cells; etc.

In one embodiment, the stored energy device 122 may be sufficient toensure completion of in-progress operations to the Flash memory devices120 a-120 n stored energy device 122 may power storage device controller119A-D and associated Flash memory devices (e.g., 120 a-n) for thoseoperations, as well as for the storing of fast-write RAM to Flashmemory. Stored energy device 122 may be used to store accumulatedstatistics and other parameters kept and tracked by the Flash memorydevices 120 a-n and/or the storage device controller 119. Separatecapacitors or stored energy devices (such as smaller capacitors near orembedded within the Flash memory devices themselves) may be used forsome or all of the operations described herein.

Various schemes may be used to track and optimize the life span of thestored energy component, such as adjusting voltage levels over time,partially discharging the storage energy device 122 to measurecorresponding discharge characteristics, etc. If the available energydecreases over time, the effective available capacity of the addressablefast-write storage may be decreased to ensure that it can be writtensafely based on the currently available stored energy.

FIG. 1D illustrates a third example system 124 for data storage inaccordance with some implementations. In one embodiment, system 124includes storage controllers 125 a, 125 b. In one embodiment, storagecontrollers 125 a, 125 b are operatively coupled to Dual PCI storagedevices 119 a, 119 b and 119 c, 119 d, respectively. Storage controllers125 a, 125 b may be operatively coupled (e.g., via a storage network130) to some number of host computers 127 a-n.

In one embodiment, two storage controllers (e.g., 125 a and 125 b)provide storage services, such as a SCS) block storage array, a fileserver, an object server, a database or data analytics service, etc. Thestorage controllers 125 a, 125 b may provide services through somenumber of network interfaces (e.g., 126 a-d) to host computers 127 a-noutside of the storage system 124. Storage controllers 125 a, 125 b mayprovide integrated services or an application entirely within thestorage system 124, forming a converged storage and compute system. Thestorage controllers 125 a, 125 b may utilize the fast write memorywithin or across storage devices 119 a-d to journal in progressoperations to ensure the operations are not lost on a power failure,storage controller removal, storage controller or storage systemshutdown, or some fault of one or more software or hardware componentswithin the storage system 124.

In one embodiment, controllers 125 a, 125 b operate as PCI masters toone or the other PCI buses 128 a, 128 b. In another embodiment, 128 aand 128 b may be based on other communications standards (e.g.,HyperTransport, InfiniBand, etc.). Other storage system embodiments mayoperate storage controllers 125 a, 125 b as multi-masters for both PCIbuses 128 a, 128 b. Alternately, a PCI/NVMe/NVMf switchinginfrastructure or fabric may connect multiple storage controllers. Somestorage system embodiments may allow storage devices to communicate witheach other directly rather than communicating only with storagecontrollers. In one embodiment, a storage device controller 119 a may beoperable under direction from a storage controller 125 a to synthesizeand transfer data to be stored into Flash memory devices from data thathas been stored in RAM (e.g., RAM 121 of FIG. 1C). For example, arecalculated version of RAM content may be transferred after a storagecontroller has determined that an operation has fully committed acrossthe storage system, or when fast-write memory on the device has reacheda certain used capacity, or after a certain amount of time, to ensureimprove safety of the data or to release addressable fast-write capacityfor reuse. This mechanism may be used, for example, to avoid a secondtransfer over a bus (e.g., 128 a, 128 b) from the storage controllers125 a, 125 b. In one embodiment, a recalculation may include compressingdata, attaching indexing or other metadata, combining multiple datasegments together, performing erasure code calculations, etc.

In one embodiment, under direction from a storage controller 125 a, 125b, a storage device controller 119 a, 119 b may be operable to calculateand transfer data to other storage devices from data stored in RAM(e.g., RAM 121 of FIG. 1C) without involvement of the storagecontrollers 125 a, 125 b. This operation may be used to mirror datastored in one controller 125 a to another controller 125 b, or it couldbe used to offload compression, data aggregation, and/or erasure codingcalculations and transfers to storage devices to reduce load on storagecontrollers or the storage controller interface 129 a, 129 b to the PCIbus 128 a, 128 b.

A storage device controller 119A-D may include mechanisms forimplementing high availability primitives for use by other parts of astorage system external to the Dual PCI storage device 118. For example,reservation or exclusion primitives may be provided so that, in astorage system with two storage controllers providing a highly availablestorage service, one storage controller may prevent the other storagecontroller from accessing or continuing to access the storage device.This could be used, for example, in cases where one controller detectsthat the other controller is not functioning properly or where theinterconnect between the two storage controllers may itself not befunctioning properly.

In one embodiment, a storage system for use with Dual PCI direct mappedstorage devices with separately addressable fast write storage includessystems that manage erase blocks or groups of erase blocks as allocationunits for storing data on behalf of the storage service, or for storingmetadata (e.g., indexes, logs, etc.) associated with the storageservice, or for proper management of the storage system itself. Flashpages, which may be a few kilobytes in size, may be written as dataarrives or as the storage system is to persist data for long intervalsof time (e.g., above a defined threshold of time). To commit data morequickly, or to reduce the number of writes to the Flash memory devices,the storage controllers may first write data into the separatelyaddressable fast write storage on one more storage devices.

In one embodiment, the storage controllers 125 a, 125 b may initiate theuse of erase blocks within and across storage devices (e.g., 118) inaccordance with an age and expected remaining lifespan of the storagedevices, or based on other statistics. The storage controllers 125 a,125 b may initiate garbage collection and data migration data betweenstorage devices in accordance with pages that are no longer needed aswell as to manage Flash page and erase block lifespans and to manageoverall system performance.

In one embodiment, the storage system 124 may utilize mirroring and/orerasure coding schemes as part of storing data into addressable fastwrite storage and/or as part of writing data into allocation unitsassociated with erase blocks. Erasure codes may be used across storagedevices, as well as within erase blocks or allocation units, or withinand across Flash memory devices on a single storage device, to provideredundancy against single or multiple storage device failures or toprotect against internal corruptions of Flash memory pages resultingfrom Flash memory operations or from degradation of Flash memory cells.Mirroring and erasure coding at various levels may be used to recoverfrom multiple types of failures that occur separately or in combination.

The embodiments depicted with reference to FIGS. 2A-G illustrate astorage cluster that stores user data, such as user data originatingfrom one or more user or client systems or other sources external to thestorage cluster. The storage cluster distributes user data acrossstorage nodes housed within a chassis, or across multiple chassis, usingerasure coding and redundant copies of metadata. Erasure coding refersto a method of data protection or reconstruction in which data is storedacross a set of different locations, such as disks, storage nodes orgeographic locations. Flash memory is one type of solid-state memorythat may be integrated with the embodiments, although the embodimentsmay be extended to other types of solid-state memory or other storagemedium, including non-solid state memory. Control of storage locationsand workloads are distributed across the storage locations in aclustered peer-to-peer system. Tasks such as mediating communicationsbetween the various storage nodes, detecting when a storage node hasbecome unavailable, and balancing I/Os (inputs and outputs) across thevarious storage nodes, are all handled on a distributed basis. Data islaid out or distributed across multiple storage nodes in data fragmentsor stripes that support data recovery in some embodiments. Ownership ofdata can be reassigned within a cluster, independent of input and outputpatterns. This architecture described in more detail below allows astorage node in the cluster to fail, with the system remainingoperational, since the data can be reconstructed from other storagenodes and thus remain available for input and output operations. Invarious embodiments, a storage node may be referred to as a clusternode, a blade, or a server.

The storage cluster may be contained within a chassis, i.e., anenclosure housing one or more storage nodes. A mechanism to providepower to each storage node, such as a power distribution bus, and acommunication mechanism, such as a communication bus that enablescommunication between the storage nodes are included within the chassis.The storage cluster can run as an independent system in one locationaccording to some embodiments. In one embodiment, a chassis contains atleast two instances of both the power distribution and the communicationbus which may be enabled or disabled independently. The internalcommunication bus may be an Ethernet bus, however, other technologiessuch as PCIe, InfiniBand, and others, are equally suitable. The chassisprovides a port for an external communication bus for enablingcommunication between multiple chassis, directly or through a switch,and with client systems. The external communication may use a technologysuch as Ethernet, InfiniBand, Fibre Channel, etc. In some embodiments,the external communication bus uses different communication bustechnologies for inter-chassis and client communication. If a switch isdeployed within or between chassis, the switch may act as a translationbetween multiple protocols or technologies. When multiple chassis areconnected to define a storage cluster, the storage cluster may beaccessed by a client using either proprietary interfaces or standardinterfaces such as network file system (‘NFS’), common internet filesystem (‘CIFS’), small computer system interface (‘SCSI’) or hypertexttransfer protocol (‘HTTP’). Translation from the client protocol mayoccur at the switch, chassis external communication bus or within eachstorage node. In some embodiments, multiple chassis may be coupled orconnected to each other through an aggregator switch. A portion and/orall of the coupled or connected chassis may be designated as a storagecluster. As discussed above, each chassis can have multiple blades, eachblade has a media access control (‘MAC’) address, but the storagecluster is presented to an external network as having a single clusterIP address and a single MAC address in some embodiments.

Each storage node may be one or more storage servers and each storageserver is connected to one or more non-volatile solid state memoryunits, which may be referred to as storage units or storage devices. Oneembodiment includes a single storage server in each storage node andbetween one to eight non-volatile solid state memory units, however thisone example is not meant to be limiting. The storage server may includea processor, DRAM and interfaces for the internal communication bus andpower distribution for each of the power buses. Inside the storage node,the interfaces and storage unit share a communication bus, e.g., PCIExpress, in some embodiments. The non-volatile solid state memory unitsmay directly access the internal communication bus interface through astorage node communication bus, or request the storage node to accessthe bus interface. The non-volatile solid state memory unit contains anembedded CPU, solid state storage controller, and a quantity of solidstate mass storage, e.g., between 2-32 terabytes (‘TB’) in someembodiments. An embedded volatile storage medium, such as DRAM, and anenergy reserve apparatus are included in the non-volatile solid statememory unit. In some embodiments, the energy reserve apparatus is acapacitor, super-capacitor, or battery that enables transferring asubset of DRAM contents to a stable storage medium in the case of powerloss. In some embodiments, the non-volatile solid state memory unit isconstructed with a storage class memory, such as phase change ormagnetoresistive random access memory (‘MRAM’) that substitutes for DRAMand enables a reduced power hold-up apparatus.

One of many features of the storage nodes and non-volatile solid statestorage is the ability to proactively rebuild data in a storage cluster.The storage nodes and non-volatile solid state storage can determinewhen a storage node or non-volatile solid state storage in the storagecluster is unreachable, independent of whether there is an attempt toread data involving that storage node or non-volatile solid statestorage. The storage nodes and non-volatile solid state storage thencooperate to recover and rebuild the data in at least partially newlocations. This constitutes a proactive rebuild, in that the systemrebuilds data without waiting until the data is needed for a read accessinitiated from a client system employing the storage cluster. These andfurther details of the storage memory and operation thereof arediscussed below.

FIG. 2A is a perspective view of a storage cluster 161, with multiplestorage nodes 150 and internal solid-state memory coupled to eachstorage node to provide network attached storage or storage areanetwork, in accordance with some embodiments. A network attachedstorage, storage area network, or a storage cluster, or other storagememory, could include one or more storage clusters 161, each having oneor more storage nodes 150, in a flexible and reconfigurable arrangementof both the physical components and the amount of storage memoryprovided thereby. The storage cluster 161 is designed to fit in a rack,and one or more racks can be set up and populated as desired for thestorage memory. The storage cluster 161 has a chassis 138 havingmultiple slots 142. It should be appreciated that chassis 138 may bereferred to as a housing, enclosure, or rack unit. In one embodiment,the chassis 138 has fourteen slots 142, although other numbers of slotsare readily devised. For example, some embodiments have four slots,eight slots, sixteen slots, thirty-two slots, or other suitable numberof slots. Each slot 142 can accommodate one storage node 150 in someembodiments. Chassis 138 includes flaps 148 that can be utilized tomount the chassis 138 on a rack. Fans 144 provide air circulation forcooling of the storage nodes 150 and components thereof, although othercooling components could be used, or an embodiment could be devisedwithout cooling components. A switch fabric 146 couples storage nodes150 within chassis 138 together and to a network for communication tothe memory. In an embodiment depicted in herein, the slots 142 to theleft of the switch fabric 146 and fans 144 are shown occupied by storagenodes 150, while the slots 142 to the right of the switch fabric 146 andfans 144 are empty and available for insertion of storage node 150 forillustrative purposes. This configuration is one example, and one ormore storage nodes 150 could occupy the slots 142 in various furtherarrangements. The storage node arrangements need not be sequential oradjacent in some embodiments. Storage nodes 150 are hot pluggable,meaning that a storage node 150 can be inserted into a slot 142 in thechassis 138, or removed from a slot 142, without stopping or poweringdown the system. Upon insertion or removal of storage node 150 from slot142, the system automatically reconfigures in order to recognize andadapt to the change. Reconfiguration, in some embodiments, includesrestoring redundancy and/or rebalancing data or load.

Each storage node 150 can have multiple components. In the embodimentshown here, the storage node 150 includes a printed circuit board 159populated by a CPU 156, i.e., processor, a memory 154 coupled to the CPU156, and a non-volatile solid state storage 152 coupled to the CPU 156,although other mountings and/or components could be used in furtherembodiments. The memory 154 has instructions which are executed by theCPU 156 and/or data operated on by the CPU 156. As further explainedbelow, the non-volatile solid state storage 152 includes flash or, infurther embodiments, other types of solid-state memory.

Referring to FIG. 2A, storage cluster 161 is scalable, meaning thatstorage capacity with non-uniform storage sizes is readily added, asdescribed above. One or more storage nodes 150 can be plugged into orremoved from each chassis and the storage cluster self-configures insome embodiments. Plug-in storage nodes 150, whether installed in achassis as delivered or later added, can have different sizes. Forexample, in one embodiment a storage node 150 can have any multiple of 4TB, e.g., 8 TB, 12 TB, 16 TB, 32 TB, etc. In further embodiments, astorage node 150 could have any multiple of other storage amounts orcapacities. Storage capacity of each storage node 150 is broadcast, andinfluences decisions of how to stripe the data. For maximum storageefficiency, an embodiment can self-configure as wide as possible in thestripe, subject to a predetermined requirement of continued operationwith loss of up to one, or up to two, non-volatile solid state storageunits 152 or storage nodes 150 within the chassis.

FIG. 2B is a block diagram showing a communications interconnect 173 andpower distribution bus 172 coupling multiple storage nodes 150.Referring back to FIG. 2A, the communications interconnect 173 can beincluded in or implemented with the switch fabric 146 in someembodiments. Where multiple storage clusters 161 occupy a rack, thecommunications interconnect 173 can be included in or implemented with atop of rack switch, in some embodiments. As illustrated in FIG. 2B,storage cluster 161 is enclosed within a single chassis 138. Externalport 176 is coupled to storage nodes 150 through communicationsinterconnect 173, while external port 174 is coupled directly to astorage node. External power port 178 is coupled to power distributionbus 172. Storage nodes 150 may include varying amounts and differingcapacities of non-volatile solid state storage 152 as described withreference to FIG. 2A. In addition, one or more storage nodes 150 may bea compute only storage node as illustrated in FIG. 2B. Authorities 168are implemented on the non-volatile solid state storages 152, forexample as lists or other data structures stored in memory. In someembodiments the authorities are stored within the non-volatile solidstate storage 152 and supported by software executing on a controller orother processor of the non-volatile solid state storage 152. In afurther embodiment, authorities 168 are implemented on the storage nodes150, for example as lists or other data structures stored in the memory154 and supported by software executing on the CPU 156 of the storagenode 150. Authorities 168 control how and where data is stored in thenon-volatile solid state storages 152 in some embodiments. This controlassists in determining which type of erasure coding scheme is applied tothe data, and which storage nodes 150 have which portions of the data.Each authority 168 may be assigned to a non-volatile solid state storage152. Each authority may control a range of inode numbers, segmentnumbers, or other data identifiers which are assigned to data by a filesystem, by the storage nodes 150, or by the non-volatile solid statestorage 152, in various embodiments.

Every piece of data, and every piece of metadata, has redundancy in thesystem in some embodiments. In addition, every piece of data and everypiece of metadata has an owner, which may be referred to as anauthority. If that authority is unreachable, for example through failureof a storage node, there is a plan of succession for how to find thatdata or that metadata. In various embodiments, there are redundantcopies of authorities 168. Authorities 168 have a relationship tostorage nodes 150 and non-volatile solid state storage 152 in someembodiments. Each authority 168, covering a range of data segmentnumbers or other identifiers of the data, may be assigned to a specificnon-volatile solid state storage 152. In some embodiments theauthorities 168 for all of such ranges are distributed over thenon-volatile solid state storages 152 of a storage cluster. Each storagenode 150 has a network port that provides access to the non-volatilesolid state storage(s) 152 of that storage node 150. Data can be storedin a segment, which is associated with a segment number and that segmentnumber is an indirection for a configuration of a RAID (redundant arrayof independent disks) stripe in some embodiments. The assignment and useof the authorities 168 thus establishes an indirection to data.Indirection may be referred to as the ability to reference dataindirectly, in this case via an authority 168, in accordance with someembodiments. A segment identifies a set of non-volatile solid statestorage 152 and a local identifier into the set of non-volatile solidstate storage 152 that may contain data. In some embodiments, the localidentifier is an offset into the device and may be reused sequentiallyby multiple segments. In other embodiments the local identifier isunique for a specific segment and never reused. The offsets in thenon-volatile solid state storage 152 are applied to locating data forwriting to or reading from the non-volatile solid state storage 152 (inthe form of a RAID stripe). Data is striped across multiple units ofnon-volatile solid state storage 152, which may include or be differentfrom the non-volatile solid state storage 152 having the authority 168for a particular data segment.

If there is a change in where a particular segment of data is located,e.g., during a data move or a data reconstruction, the authority 168 forthat data segment should be consulted, at that non-volatile solid statestorage 152 or storage node 150 having that authority 168. In order tolocate a particular piece of data, embodiments calculate a hash valuefor a data segment or apply an inode number or a data segment number.The output of this operation points to a non-volatile solid statestorage 152 having the authority 168 for that particular piece of data.In some embodiments there are two stages to this operation. The firststage maps an entity identifier (ID), e.g., a segment number, inodenumber, or directory number to an authority identifier. This mapping mayinclude a calculation such as a hash or a bit mask. The second stage ismapping the authority identifier to a particular non-volatile solidstate storage 152, which may be done through an explicit mapping. Theoperation is repeatable, so that when the calculation is performed, theresult of the calculation repeatably and reliably points to a particularnon-volatile solid state storage 152 having that authority 168. Theoperation may include the set of reachable storage nodes as input. Ifthe set of reachable non-volatile solid state storage units changes theoptimal set changes. In some embodiments, the persisted value is thecurrent assignment (which is always true) and the calculated value isthe target assignment the cluster will attempt to reconfigure towards.This calculation may be used to determine the optimal non-volatile solidstate storage 152 for an authority in the presence of a set ofnon-volatile solid state storage 152 that are reachable and constitutethe same cluster. The calculation also determines an ordered set of peernon-volatile solid state storage 152 that will also record the authorityto non-volatile solid state storage mapping so that the authority may bedetermined even if the assigned non-volatile solid state storage isunreachable. A duplicate or substitute authority 168 may be consulted ifa specific authority 168 is unavailable in some embodiments.

With reference to FIGS. 2A and 2B, two of the many tasks of the CPU 156on a storage node 150 are to break up write data, and reassemble readdata. When the system has determined that data is to be written, theauthority 168 for that data is located as above. When the segment ID fordata is already determined the request to write is forwarded to thenon-volatile solid state storage 152 currently determined to be the hostof the authority 168 determined from the segment. The host CPU 156 ofthe storage node 150, on which the non-volatile solid state storage 152and corresponding authority 168 reside, then breaks up or shards thedata and transmits the data out to various non-volatile solid statestorage 152. The transmitted data is written as a data stripe inaccordance with an erasure coding scheme. In some embodiments, data isrequested to be pulled, and in other embodiments, data is pushed. Inreverse, when data is read, the authority 168 for the segment IDcontaining the data is located as described above. The host CPU 156 ofthe storage node 150 on which the non-volatile solid state storage 152and corresponding authority 168 reside requests the data from thenon-volatile solid state storage and corresponding storage nodes pointedto by the authority. In some embodiments the data is read from flashstorage as a data stripe. The host CPU 156 of storage node 150 thenreassembles the read data, correcting any errors (if present) accordingto the appropriate erasure coding scheme, and forwards the reassembleddata to the network. In further embodiments, some or all of these taskscan be handled in the non-volatile solid state storage 152. In someembodiments, the segment host requests the data be sent to storage node150 by requesting pages from storage and then sending the data to thestorage node making the original request.

In some systems, for example in UNIX-style file systems, data is handledwith an index node or inode, which specifies a data structure thatrepresents an object in a file system. The object could be a file or adirectory, for example. Metadata may accompany the object, as attributessuch as permission data and a creation timestamp, among otherattributes. A segment number could be assigned to all or a portion ofsuch an object in a file system. In other systems, data segments arehandled with a segment number assigned elsewhere. For purposes ofdiscussion, the unit of distribution is an entity, and an entity can bea file, a directory or a segment. That is, entities are units of data ormetadata stored by a storage system. Entities are grouped into setscalled authorities. Each authority has an authority owner, which is astorage node that has the exclusive right to update the entities in theauthority. In other words, a storage node contains the authority, andthat the authority, in turn, contains entities.

A segment is a logical container of data in accordance with someembodiments. A segment is an address space between medium address spaceand physical flash locations, i.e., the data segment number, are in thisaddress space. Segments may also contain meta-data, which enable dataredundancy to be restored (rewritten to different flash locations ordevices) without the involvement of higher level software. In oneembodiment, an internal format of a segment contains client data andmedium mappings to determine the position of that data. Each datasegment is protected, e.g., from memory and other failures, by breakingthe segment into a number of data and parity shards, where applicable.The data and parity shards are distributed, i.e., striped, acrossnon-volatile solid state storage 152 coupled to the host CPUs 156 (SeeFIGS. 2E and 2G) in accordance with an erasure coding scheme. Usage ofthe term segments refers to the container and its place in the addressspace of segments in some embodiments. Usage of the term stripe refersto the same set of shards as a segment and includes how the shards aredistributed along with redundancy or parity information in accordancewith some embodiments.

A series of address-space transformations takes place across an entirestorage system. At the top are the directory entries (file names) whichlink to an inode. Inodes point into medium address space, where data islogically stored. Medium addresses may be mapped through a series ofindirect mediums to spread the load of large files, or implement dataservices like deduplication or snapshots. Medium addresses may be mappedthrough a series of indirect mediums to spread the load of large files,or implement data services like deduplication or snapshots. Segmentaddresses are then translated into physical flash locations. Physicalflash locations have an address range bounded by the amount of flash inthe system in accordance with some embodiments. Medium addresses andsegment addresses are logical containers, and in some embodiments use a128 bit or larger identifier so as to be practically infinite, with alikelihood of reuse calculated as longer than the expected life of thesystem. Addresses from logical containers are allocated in ahierarchical fashion in some embodiments. Initially, each non-volatilesolid state storage unit 152 may be assigned a range of address space.Within this assigned range, the non-volatile solid state storage 152 isable to allocate addresses without synchronization with othernon-volatile solid state storage 152.

Data and metadata is stored by a set of underlying storage layouts thatare optimized for varying workload patterns and storage devices. Theselayouts incorporate multiple redundancy schemes, compression formats andindex algorithms. Some of these layouts store information aboutauthorities and authority masters, while others store file metadata andfile data. The redundancy schemes include error correction codes thattolerate corrupted bits within a single storage device (such as a NANDflash chip), erasure codes that tolerate the failure of multiple storagenodes, and replication schemes that tolerate data center or regionalfailures. In some embodiments, low density parity check (‘LDPC’) code isused within a single storage unit. Reed-Solomon encoding is used withina storage cluster, and mirroring is used within a storage grid in someembodiments. Metadata may be stored using an ordered log structuredindex (such as a Log Structured Merge Tree), and large data may not bestored in a log structured layout.

In order to maintain consistency across multiple copies of an entity,the storage nodes agree implicitly on two things through calculations:(1) the authority that contains the entity, and (2) the storage nodethat contains the authority. The assignment of entities to authoritiescan be done by pseudo randomly assigning entities to authorities, bysplitting entities into ranges based upon an externally produced key, orby placing a single entity into each authority. Examples of pseudorandomschemes are linear hashing and the Replication Under Scalable Hashing(‘RUSH’) family of hashes, including Controlled Replication UnderScalable Hashing (‘CRUSH’). In some embodiments, pseudorandom assignmentis utilized only for assigning authorities to nodes because the set ofnodes can change. The set of authorities cannot change so any subjectivefunction may be applied in these embodiments. Some placement schemesautomatically place authorities on storage nodes, while other placementschemes rely on an explicit mapping of authorities to storage nodes. Insome embodiments, a pseudorandom scheme is utilized to map from eachauthority to a set of candidate authority owners. A pseudorandom datadistribution function related to CRUSH may assign authorities to storagenodes and create a list of where the authorities are assigned. Eachstorage node has a copy of the pseudorandom data distribution function,and can arrive at the same calculation for distributing, and laterfinding or locating an authority. Each of the pseudorandom schemesrequires the reachable set of storage nodes as input in some embodimentsin order to conclude the same target nodes. Once an entity has beenplaced in an authority, the entity may be stored on physical devices sothat no expected failure will lead to unexpected data loss. In someembodiments, rebalancing algorithms attempt to store the copies of allentities within an authority in the same layout and on the same set ofmachines.

Examples of expected failures include device failures, stolen machines,datacenter fires, and regional disasters, such as nuclear or geologicalevents. Different failures lead to different levels of acceptable dataloss. In some embodiments, a stolen storage node impacts neither thesecurity nor the reliability of the system, while depending on systemconfiguration, a regional event could lead to no loss of data, a fewseconds or minutes of lost updates, or even complete data loss.

In the embodiments, the placement of data for storage redundancy isindependent of the placement of authorities for data consistency. Insome embodiments, storage nodes that contain authorities do not containany persistent storage. Instead, the storage nodes are connected tonon-volatile solid state storage units that do not contain authorities.The communications interconnect between storage nodes and non-volatilesolid state storage units consists of multiple communicationtechnologies and has non-uniform performance and fault tolerancecharacteristics. In some embodiments, as mentioned above, non-volatilesolid state storage units are connected to storage nodes via PCIexpress, storage nodes are connected together within a single chassisusing Ethernet backplane, and chassis are connected together to form astorage cluster. Storage clusters are connected to clients usingEthernet or fiber channel in some embodiments. If multiple storageclusters are configured into a storage grid, the multiple storageclusters are connected using the Internet or other long-distancenetworking links, such as a “metro scale” link or private link that doesnot traverse the internet.

Authority owners have the exclusive right to modify entities, to migrateentities from one non-volatile solid state storage unit to anothernon-volatile solid state storage unit, and to add and remove copies ofentities. This allows for maintaining the redundancy of the underlyingdata. When an authority owner fails, is going to be decommissioned, oris overloaded, the authority is transferred to a new storage node.Transient failures make it non-trivial to ensure that all non-faultymachines agree upon the new authority location. The ambiguity thatarises due to transient failures can be achieved automatically by aconsensus protocol such as Paxos, hot-warm failover schemes, via manualintervention by a remote system administrator, or by a local hardwareadministrator (such as by physically removing the failed machine fromthe cluster, or pressing a button on the failed machine). In someembodiments, a consensus protocol is used, and failover is automatic. Iftoo many failures or replication events occur in too short a timeperiod, the system goes into a self-preservation mode and haltsreplication and data movement activities until an administratorintervenes in accordance with some embodiments.

As authorities are transferred between storage nodes and authorityowners update entities in their authorities, the system transfersmessages between the storage nodes and non-volatile solid state storageunits. With regard to persistent messages, messages that have differentpurposes are of different types. Depending on the type of the message,the system maintains different ordering and durability guarantees. Asthe persistent messages are being processed, the messages aretemporarily stored in multiple durable and non-durable storage hardwaretechnologies. In some embodiments, messages are stored in RAM, NVRAM andon NAND flash devices, and a variety of protocols are used in order tomake efficient use of each storage medium. Latency-sensitive clientrequests may be persisted in replicated NVRAM, and then later NAND,while background rebalancing operations are persisted directly to NAND.

Persistent messages are persistently stored prior to being transmitted.This allows the system to continue to serve client requests despitefailures and component replacement. Although many hardware componentscontain unique identifiers that are visible to system administrators,manufacturer, hardware supply chain and ongoing monitoring qualitycontrol infrastructure, applications running on top of theinfrastructure address virtualize addresses. These virtualized addressesdo not change over the lifetime of the storage system, regardless ofcomponent failures and replacements. This allows each component of thestorage system to be replaced over time without reconfiguration ordisruptions of client request processing, i.e., the system supportsnon-disruptive upgrades.

In some embodiments, the virtualized addresses are stored withsufficient redundancy. A continuous monitoring system correlateshardware and software status and the hardware identifiers. This allowsdetection and prediction of failures due to faulty components andmanufacturing details. The monitoring system also enables the proactivetransfer of authorities and entities away from impacted devices beforefailure occurs by removing the component from the critical path in someembodiments.

FIG. 2C is a multiple level block diagram, showing contents of a storagenode 150 and contents of a non-volatile solid state storage 152 of thestorage node 150. Data is communicated to and from the storage node 150by a network interface controller (‘NIC’) 202 in some embodiments. Eachstorage node 150 has a CPU 156, and one or more non-volatile solid statestorage 152, as discussed above. Moving down one level in FIG. 2C, eachnon-volatile solid state storage 152 has a relatively fast non-volatilesolid state memory, such as nonvolatile random access memory (‘NVRAM’)204, and flash memory 206. In some embodiments, NVRAM 204 may be acomponent that does not require program/erase cycles (DRAM, MRAM, PCM),and can be a memory that can support being written vastly more oftenthan the memory is read from. Moving down another level in FIG. 2C, theNVRAM 204 is implemented in one embodiment as high speed volatilememory, such as dynamic random access memory (DRAM) 216, backed up byenergy reserve 218. Energy reserve 218 provides sufficient electricalpower to keep the DRAM 216 powered long enough for contents to betransferred to the flash memory 206 in the event of power failure. Insome embodiments, energy reserve 218 is a capacitor, super-capacitor,battery, or other device, that supplies a suitable supply of energysufficient to enable the transfer of the contents of DRAM 216 to astable storage medium in the case of power loss. The flash memory 206 isimplemented as multiple flash dies 222, which may be referred to aspackages of flash dies 222 or an array of flash dies 222. It should beappreciated that the flash dies 222 could be packaged in any number ofways, with a single die per package, multiple dies per package (i.e.multichip packages), in hybrid packages, as bare dies on a printedcircuit board or other substrate, as encapsulated dies, etc. In theembodiment shown, the non-volatile solid state storage 152 has acontroller 212 or other processor, and an input output (I/O) port 210coupled to the controller 212. I/O port 210 is coupled to the CPU 156and/or the network interface controller 202 of the flash storage node150. Flash input output (I/O) port 220 is coupled to the flash dies 222,and a direct memory access unit (DMA) 214 is coupled to the controller212, the DRAM 216 and the flash dies 222. In the embodiment shown, theI/O port 210, controller 212, DMA unit 214 and flash I/O port 220 areimplemented on a programmable logic device (‘PLD’) 208, e.g., an FPGA.In this embodiment, each flash die 222 has pages, organized as sixteenkB (kilobyte) pages 224, and a register 226 through which data can bewritten to or read from the flash die 222. In further embodiments, othertypes of solid-state memory are used in place of, or in addition toflash memory illustrated within flash die 222.

Storage clusters 161, in various embodiments as disclosed herein, can becontrasted with storage arrays in general. The storage nodes 150 arepart of a collection that creates the storage cluster 161. Each storagenode 150 owns a slice of data and computing required to provide thedata. Multiple storage nodes 150 cooperate to store and retrieve thedata. Storage memory or storage devices, as used in storage arrays ingeneral, are less involved with processing and manipulating the data.Storage memory or storage devices in a storage array receive commands toread, write, or erase data. The storage memory or storage devices in astorage array are not aware of a larger system in which they areembedded, or what the data means. Storage memory or storage devices instorage arrays can include various types of storage memory, such as RAM,solid state drives, hard disk drives, etc. The storage units 152described herein have multiple interfaces active simultaneously andserving multiple purposes. In some embodiments, some of thefunctionality of a storage node 150 is shifted into a storage unit 152,transforming the storage unit 152 into a combination of storage unit 152and storage node 150. Placing computing (relative to storage data) intothe storage unit 152 places this computing closer to the data itself.The various system embodiments have a hierarchy of storage node layerswith different capabilities. By contrast, in a storage array, acontroller owns and knows everything about all of the data that thecontroller manages in a shelf or storage devices. In a storage cluster161, as described herein, multiple controllers in multiple storage units152 and/or storage nodes 150 cooperate in various ways (e.g., forerasure coding, data sharding, metadata communication and redundancy,storage capacity expansion or contraction, data recovery, and so on).

FIG. 2D shows a storage server environment, which uses embodiments ofthe storage nodes 150 and storage units 152 of FIGS. 2A-C. In thisversion, each storage unit 152 has a processor such as controller 212(see FIG. 2C), an FPGA, flash memory 206, and NVRAM 204 (which issuper-capacitor backed DRAM 216, see FIGS. 2B and 2C) on a PCIe(peripheral component interconnect express) board in a chassis 138 (seeFIG. 2A). The storage unit 152 may be implemented as a single boardcontaining storage, and may be the largest tolerable failure domaininside the chassis. In some embodiments, up to two storage units 152 mayfail and the device will continue with no data loss.

The physical storage is divided into named regions based on applicationusage in some embodiments. The NVRAM 204 is a contiguous block ofreserved memory in the storage unit 152 DRAM 216, and is backed by NANDflash. NVRAM 204 is logically divided into multiple memory regionswritten for two as spool (e.g., spool_region). Space within the NVRAM204 spools is managed by each authority 168 independently. Each deviceprovides an amount of storage space to each authority 168. Thatauthority 168 further manages lifetimes and allocations within thatspace. Examples of a spool include distributed transactions or notions.When the primary power to a storage unit 152 fails, onboardsuper-capacitors provide a short duration of power hold up. During thisholdup interval, the contents of the NVRAM 204 are flushed to flashmemory 206. On the next power-on, the contents of the NVRAM 204 arerecovered from the flash memory 206.

As for the storage unit controller, the responsibility of the logical“controller” is distributed across each of the blades containingauthorities 168. This distribution of logical control is shown in FIG.2D as a host controller 242, mid-tier controller 244 and storage unitcontroller(s) 246. Management of the control plane and the storage planeare treated independently, although parts may be physically co-locatedon the same blade. Each authority 168 effectively serves as anindependent controller. Each authority 168 provides its own data andmetadata structures, its own background workers, and maintains its ownlifecycle.

FIG. 2E is a blade 252 hardware block diagram, showing a control plane254, compute and storage planes 256, 258, and authorities 168interacting with underlying physical resources, using embodiments of thestorage nodes 150 and storage units 152 of FIGS. 2A-C in the storageserver environment of FIG. 2D. The control plane 254 is partitioned intoa number of authorities 168 which can use the compute resources in thecompute plane 256 to run on any of the blades 252. The storage plane 258is partitioned into a set of devices, each of which provides access toflash 206 and NVRAM 204 resources. In one embodiment, the compute plane256 may perform the operations of a storage array controller, asdescribed herein, on one or more devices of the storage plane 258 (e.g.,a storage array).

In the compute and storage planes 256, 258 of FIG. 2E, the authorities168 interact with the underlying physical resources (i.e., devices).From the point of view of an authority 168, its resources are stripedover all of the physical devices. From the point of view of a device, itprovides resources to all authorities 168, irrespective of where theauthorities happen to run. Each authority 168 has allocated or has beenallocated one or more partitions 260 of storage memory in the storageunits 152, e.g. partitions 260 in flash memory 206 and NVRAM 204. Eachauthority 168 uses those allocated partitions 260 that belong to it, forwriting or reading user data. Authorities can be associated withdiffering amounts of physical storage of the system. For example, oneauthority 168 could have a larger number of partitions 260 or largersized partitions 260 in one or more storage units 152 than one or moreother authorities 168.

FIG. 2F depicts elasticity software layers in blades 252 of a storagecluster, in accordance with some embodiments. In the elasticitystructure, elasticity software is symmetric, i.e., each blade's computemodule 270 runs the three identical layers of processes depicted in FIG.2F. Storage managers 274 execute read and write requests from otherblades 252 for data and metadata stored in local storage unit 152 NVRAM204 and flash 206. Authorities 168 fulfill client requests by issuingthe necessary reads and writes to the blades 252 on whose storage units152 the corresponding data or metadata resides. Endpoints 272 parseclient connection requests received from switch fabric 146 supervisorysoftware, relay the client connection requests to the authorities 168responsible for fulfillment, and relay the authorities' 168 responses toclients. The symmetric three-layer structure enables the storagesystem's high degree of concurrency. Elasticity scales out efficientlyand reliably in these embodiments. In addition, elasticity implements aunique scale-out technique that balances work evenly across allresources regardless of client access pattern, and maximizes concurrencyby eliminating much of the need for inter-blade coordination thattypically occurs with conventional distributed locking.

Still referring to FIG. 2F, authorities 168 running in the computemodules 270 of a blade 252 perform the internal operations required tofulfill client requests. One feature of elasticity is that authorities168 are stateless, i.e., they cache active data and metadata in theirown blades' 252 DRAMs for fast access, but the authorities store everyupdate in their NVRAM 204 partitions on three separate blades 252 untilthe update has been written to flash 206. All the storage system writesto NVRAM 204 are in triplicate to partitions on three separate blades252 in some embodiments. With triple-mirrored NVRAM 204 and persistentstorage protected by parity and Reed-Solomon RAID checksums, the storagesystem can survive concurrent failure of two blades 252 with no loss ofdata, metadata, or access to either.

Because authorities 168 are stateless, they can migrate between blades252. Each authority 168 has a unique identifier. NVRAM 204 and flash 206partitions are associated with authorities' 168 identifiers, not withthe blades 252 on which they are running in some. Thus, when anauthority 168 migrates, the authority 168 continues to manage the samestorage partitions from its new location. When a new blade 252 isinstalled in an embodiment of the storage cluster, the systemautomatically rebalances load by: partitioning the new blade's 252storage for use by the system's authorities 168, migrating selectedauthorities 168 to the new blade 252, starting endpoints 272 on the newblade 252 and including them in the switch fabric's 146 clientconnection distribution algorithm.

From their new locations, migrated authorities 168 persist the contentsof their NVRAM 204 partitions on flash 206, process read and writerequests from other authorities 168, and fulfill the client requeststhat endpoints 272 direct to them. Similarly, if a blade 252 fails or isremoved, the system redistributes its authorities 168 among the system'sremaining blades 252. The redistributed authorities 168 continue toperform their original functions from their new locations.

FIG. 2G depicts authorities 168 and storage resources in blades 252 of astorage cluster, in accordance with some embodiments. Each authority 168is exclusively responsible for a partition of the flash 206 and NVRAM204 on each blade 252. The authority 168 manages the content andintegrity of its partitions independently of other authorities 168.Authorities 168 compress incoming data and preserve it temporarily intheir NVRAM 204 partitions, and then consolidate, RAID-protect, andpersist the data in segments of the storage in their flash 206partitions. As the authorities 168 write data to flash 206, storagemanagers 274 perform the necessary flash translation to optimize writeperformance and maximize media longevity. In the background, authorities168 “garbage collect,” or reclaim space occupied by data that clientshave made obsolete by overwriting the data. It should be appreciatedthat since authorities' 168 partitions are disjoint, there is no needfor distributed locking to execute client and writes or to performbackground functions.

The embodiments described herein may utilize various software,communication and/or networking protocols. In addition, theconfiguration of the hardware and/or software may be adjusted toaccommodate various protocols. For example, the embodiments may utilizeActive Directory, which is a database based system that providesauthentication, directory, policy, and other services in a WINDOWS™environment. In these embodiments, LDAP (Lightweight Directory AccessProtocol) is one example application protocol for querying and modifyingitems in directory service providers such as Active Directory. In someembodiments, a network lock manager (‘NLM’) is utilized as a facilitythat works in cooperation with the Network File System (‘NFS’) toprovide a System V style of advisory file and record locking over anetwork. The Server Message Block (‘SMB’) protocol, one version of whichis also known as Common Internet File System (‘CIFS’), may be integratedwith the storage systems discussed herein. SMP operates as anapplication-layer network protocol typically used for providing sharedaccess to files, printers, and serial ports and miscellaneouscommunications between nodes on a network. SMB also provides anauthenticated inter-process communication mechanism. AMAZON™ S3 (SimpleStorage Service) is a web service offered by Amazon Web Services, andthe systems described herein may interface with Amazon S3 through webservices interfaces (REST (representational state transfer), SOAP(simple object access protocol), and BitTorrent). A RESTful API(application programming interface) breaks down a transaction to createa series of small modules. Each module addresses a particular underlyingpart of the transaction. The control or permissions provided with theseembodiments, especially for object data, may include utilization of anaccess control list (‘ACL’). The ACL is a list of permissions attachedto an object and the ACL specifies which users or system processes aregranted access to objects, as well as what operations are allowed ongiven objects. The systems may utilize Internet Protocol version 6(‘IPv6’), as well as IPv4, for the communications protocol that providesan identification and location system for computers on networks androutes traffic across the Internet. The routing of packets betweennetworked systems may include Equal-cost multi-path routing (‘ECMP’),which is a routing strategy where next-hop packet forwarding to a singledestination can occur over multiple “best paths” which tie for top placein routing metric calculations. Multi-path routing can be used inconjunction with most routing protocols, because it is a per-hopdecision limited to a single router. The software may supportMulti-tenancy, which is an architecture in which a single instance of asoftware application serves multiple customers. Each customer may bereferred to as a tenant. Tenants may be given the ability to customizesome parts of the application, but may not customize the application'scode, in some embodiments. The embodiments may maintain audit logs. Anaudit log is a document that records an event in a computing system. Inaddition to documenting what resources were accessed, audit log entriestypically include destination and source addresses, a timestamp, anduser login information for compliance with various regulations. Theembodiments may support various key management policies, such asencryption key rotation. In addition, the system may support dynamicroot passwords or some variation dynamically changing passwords.

FIG. 3A sets forth a diagram of a storage system 306 that is coupled fordata communications with a cloud services provider 302 in accordancewith some embodiments of the present disclosure. Although depicted inless detail, the storage system 306 depicted in FIG. 3A may be similarto the storage systems described above with reference to FIGS. 1A-1D andFIGS. 2A-2G. In some embodiments, the storage system 306 depicted inFIG. 3A may be embodied as a storage system that includes imbalancedactive/active controllers, as a storage system that includes balancedactive/active controllers, as a storage system that includesactive/active controllers where less than all of each controller'sresources are utilized such that each controller has reserve resourcesthat may be used to support failover, as a storage system that includesfully active/active controllers, as a storage system that includesdataset-segregated controllers, as a storage system that includesdual-layer architectures with frontend controllers and back-endintegrated storage controllers, as a storage system that includesscale-out clusters of dual-controller arrays, as well as combinations ofsuch embodiments.

In the example depicted in FIG. 3A, the storage system 306 is coupled tothe cloud services provider 302 via a data communications link 304. Thedata communications link 304 may be embodied as a dedicated datacommunications link, as a data communications pathway that is providedthrough the use of one or data communications networks such as a widearea network (‘WAN’) or LAN, or as some other mechanism capable oftransporting digital information between the storage system 306 and thecloud services provider 302. Such a data communications link 304 may befully wired, fully wireless, or some aggregation of wired and wirelessdata communications pathways. In such an example, digital informationmay be exchanged between the storage system 306 and the cloud servicesprovider 302 via the data communications link 304 using one or more datacommunications protocols. For example, digital information may beexchanged between the storage system 306 and the cloud services provider302 via the data communications link 304 using the handheld devicetransfer protocol (‘HDTP’), hypertext transfer protocol (‘HTTP’),internet protocol (‘IP’), real-time transfer protocol (‘RTP’),transmission control protocol (‘TCP’), user datagram protocol (‘UDP’),wireless application protocol (‘WAP’), or other protocol.

The cloud services provider 302 depicted in FIG. 3A may be embodied, forexample, as a system and computing environment that provides a vastarray of services to users of the cloud services provider 302 throughthe sharing of computing resources via the data communications link 304.The cloud services provider 302 may provide on-demand access to a sharedpool of configurable computing resources such as computer networks,servers, storage, applications and services, and so on. The shared poolof configurable resources may be rapidly provisioned and released to auser of the cloud services provider 302 with minimal management effort.Generally, the user of the cloud services provider 302 is unaware of theexact computing resources utilized by the cloud services provider 302 toprovide the services. Although in many cases such a cloud servicesprovider 302 may be accessible via the Internet, readers of skill in theart will recognize that any system that abstracts the use of sharedresources to provide services to a user through any data communicationslink may be considered a cloud services provider 302.

In the example depicted in FIG. 3A, the cloud services provider 302 maybe configured to provide a variety of services to the storage system 306and users of the storage system 306 through the implementation ofvarious service models. For example, the cloud services provider 302 maybe configured to provide services through the implementation of aninfrastructure as a service (‘IaaS’) service model, through theimplementation of a platform as a service (‘PaaS’) service model,through the implementation of a software as a service (‘SaaS’) servicemodel, through the implementation of an authentication as a service(‘AaaS’) service model, through the implementation of a storage as aservice model where the cloud services provider 302 offers access to itsstorage infrastructure for use by the storage system 306 and users ofthe storage system 306, and so on. Readers will appreciate that thecloud services provider 302 may be configured to provide additionalservices to the storage system 306 and users of the storage system 306through the implementation of additional service models, as the servicemodels described above are included only for explanatory purposes and inno way represent a limitation of the services that may be offered by thecloud services provider 302 or a limitation as to the service modelsthat may be implemented by the cloud services provider 302.

In the example depicted in FIG. 3A, the cloud services provider 302 maybe embodied, for example, as a private cloud, as a public cloud, or as acombination of a private cloud and public cloud. In an embodiment inwhich the cloud services provider 302 is embodied as a private cloud,the cloud services provider 302 may be dedicated to providing servicesto a single organization rather than providing services to multipleorganizations. In an embodiment where the cloud services provider 302 isembodied as a public cloud, the cloud services provider 302 may provideservices to multiple organizations. In still alternative embodiments,the cloud services provider 302 may be embodied as a mix of a privateand public cloud services with a hybrid cloud deployment.

Although not explicitly depicted in FIG. 3A, readers will appreciatethat a vast amount of additional hardware components and additionalsoftware components may be necessary to facilitate the delivery of cloudservices to the storage system 306 and users of the storage system 306.For example, the storage system 306 may be coupled to (or even include)a cloud storage gateway. Such a cloud storage gateway may be embodied,for example, as hardware-based or software-based appliance that islocated on premise with the storage system 306. Such a cloud storagegateway may operate as a bridge between local applications that areexecuting on the storage array 306 and remote, cloud-based storage thatis utilized by the storage array 306. Through the use of a cloud storagegateway, organizations may move primary iSCSI or NAS to the cloudservices provider 302, thereby enabling the organization to save spaceon their on-premises storage systems. Such a cloud storage gateway maybe configured to emulate a disk array, a block-based device, a fileserver, or other storage system that can translate the SCSI commands,file server commands, or other appropriate command into REST-spaceprotocols that facilitate communications with the cloud servicesprovider 302.

In order to enable the storage system 306 and users of the storagesystem 306 to make use of the services provided by the cloud servicesprovider 302, a cloud migration process may take place during whichdata, applications, or other elements from an organization's localsystems (or even from another cloud environment) are moved to the cloudservices provider 302. In order to successfully migrate data,applications, or other elements to the cloud services provider's 302environment, middleware such as a cloud migration tool may be utilizedto bridge gaps between the cloud services provider's 302 environment andan organization's environment. Such cloud migration tools may also beconfigured to address potentially high network costs and long transfertimes associated with migrating large volumes of data to the cloudservices provider 302, as well as addressing security concernsassociated with sensitive data to the cloud services provider 302 overdata communications networks. In order to further enable the storagesystem 306 and users of the storage system 306 to make use of theservices provided by the cloud services provider 302, a cloudorchestrator may also be used to arrange and coordinate automated tasksin pursuit of creating a consolidated process or workflow. Such a cloudorchestrator may perform tasks such as configuring various components,whether those components are cloud components or on-premises components,as well as managing the interconnections between such components. Thecloud orchestrator can simplify the inter-component communication andconnections to ensure that links are correctly configured andmaintained.

In the example depicted in FIG. 3A, and as described briefly above, thecloud services provider 302 may be configured to provide services to thestorage system 306 and users of the storage system 306 through the usageof a SaaS service model, eliminating the need to install and run theapplication on local computers, which may simplify maintenance andsupport of the application. Such applications may take many forms inaccordance with various embodiments of the present disclosure. Forexample, the cloud services provider 302 may be configured to provideaccess to data analytics applications to the storage system 306 andusers of the storage system 306. Such data analytics applications may beconfigured, for example, to receive vast amounts of telemetry dataphoned home by the storage system 306. Such telemetry data may describevarious operating characteristics of the storage system 306 and may beanalyzed for a vast array of purposes including, for example, todetermine the health of the storage system 306, to identify workloadsthat are executing on the storage system 306, to predict when thestorage system 306 will run out of various resources, to recommendconfiguration changes, hardware or software upgrades, workflowmigrations, or other actions that may improve the operation of thestorage system 306.

The cloud services provider 302 may also be configured to provide accessto virtualized computing environments to the storage system 306 andusers of the storage system 306. Such virtualized computing environmentsmay be embodied, for example, as a virtual machine or other virtualizedcomputer hardware platforms, virtual storage devices, virtualizedcomputer network resources, and so on. Examples of such virtualizedenvironments can include virtual machines that are created to emulate anactual computer, virtualized desktop environments that separate alogical desktop from a physical machine, virtualized file systems thatallow uniform access to different types of concrete file systems, andmany others.

For further explanation, FIG. 3B sets forth a diagram of a storagesystem 306 in accordance with some embodiments of the presentdisclosure. Although depicted in less detail, the storage system 306depicted in FIG. 3B may be similar to the storage systems describedabove with reference to FIGS. 1A-1D and FIGS. 2A-2G as the storagesystem may include many of the components described above.

The storage system 306 depicted in FIG. 3B may include a vast amount ofstorage resources 308, which may be embodied in many forms. For example,the storage resources 308 can include nano-RAM or another form ofnonvolatile random access memory that utilizes carbon nanotubesdeposited on a substrate, 3D crosspoint non-volatile memory, flashmemory including single-level cell (‘SLC’) NAND flash, multi-level cell(‘MLC’) NAND flash, triple-level cell (‘TLC’) NAND flash, quad-levelcell (‘QLC’) NAND flash, or others. Likewise, the storage resources 308may include non-volatile magnetoresistive random-access memory (‘MRAM’),including spin transfer torque (‘STT’) MRAM. The example storageresources 308 may alternatively include non-volatile phase-change memory(‘PCM’), quantum memory that allows for the storage and retrieval ofphotonic quantum information, resistive random-access memory (‘ReRAM’),storage class memory (‘SCM’), or other form of storage resources,including any combination of resources described herein. Readers willappreciate that other forms of computer memories and storage devices maybe utilized by the storage systems described above, including DRAM,SRAM, EEPROM, universal memory, and many others. The storage resources308 depicted in FIG. 3A may be embodied in a variety of form factors,including but not limited to, dual in-line memory modules (‘DIMMs’),non-volatile dual in-line memory modules (‘NVDIMMs’), M.2, U.2, andothers.

The storage resources 308 depicted in FIG. 3A may include various formsof SCM. SCM may effectively treat fast, non-volatile memory (e.g., NANDflash) as an extension of DRAM such that an entire dataset may betreated as an in-memory dataset that resides entirely in DRAM. SCM mayinclude non-volatile media such as, for example, NAND flash. Such NANDflash may be accessed utilizing NVMe that can use the PCIe bus as itstransport, providing for relatively low access latencies compared toolder protocols. In fact, the network protocols used for SSDs inall-flash arrays can include NVMe using Ethernet (ROCE, NVME TCP), FibreChannel (NVMe FC), InfiniBand (iWARP), and others that make it possibleto treat fast, non-volatile memory as an extension of DRAM. In view ofthe fact that DRAM is often byte-addressable and fast, non-volatilememory such as NAND flash is block-addressable, a controllersoftware/hardware stack may be needed to convert the block data to thebytes that are stored in the media. Examples of media and software thatmay be used as SCM can include, for example, 3D XPoint, Intel MemoryDrive Technology, Samsung's Z-SSD, and others.

The example storage system 306 depicted in FIG. 3B may implement avariety of storage architectures. For example, storage systems inaccordance with some embodiments of the present disclosure may utilizeblock storage where data is stored in blocks, and each block essentiallyacts as an individual hard drive. Storage systems in accordance withsome embodiments of the present disclosure may utilize object storage,where data is managed as objects. Each object may include the dataitself, a variable amount of metadata, and a globally unique identifier,where object storage can be implemented at multiple levels (e.g., devicelevel, system level, interface level). Storage systems in accordancewith some embodiments of the present disclosure utilize file storage inwhich data is stored in a hierarchical structure. Such data may be savedin files and folders, and presented to both the system storing it andthe system retrieving it in the same format.

The example storage system 306 depicted in FIG. 3B may be embodied as astorage system in which additional storage resources can be addedthrough the use of a scale-up model, additional storage resources can beadded through the use of a scale-out model, or through some combinationthereof. In a scale-up model, additional storage may be added by addingadditional storage devices. In a scale-out model, however, additionalstorage nodes may be added to a cluster of storage nodes, where suchstorage nodes can include additional processing resources, additionalnetworking resources, and so on.

The storage system 306 depicted in FIG. 3B also includes communicationsresources 310 that may be useful in facilitating data communicationsbetween components within the storage system 306, as well as datacommunications between the storage system 306 and computing devices thatare outside of the storage system 306, including embodiments where thoseresources are separated by a relatively vast expanse. The communicationsresources 310 may be configured to utilize a variety of differentprotocols and data communication fabrics to facilitate datacommunications between components within the storage systems as well ascomputing devices that are outside of the storage system. For example,the communications resources 310 can include fibre channel (‘FC’)technologies such as FC fabrics and FC protocols that can transport SCSIcommands over FC network, FC over ethernet (‘FCoE’) technologies throughwhich FC frames are encapsulated and transmitted over Ethernet networks,InfiniBand (‘IB’) technologies in which a switched fabric topology isutilized to facilitate transmissions between channel adapters, NVMExpress (‘NVMe’) technologies and NVMe over fabrics (‘NVMeoF’)technologies through which non-volatile storage media attached via a PCIexpress (‘PCIe’) bus may be accessed, and others. In fact, the storagesystems described above may, directly or indirectly, make use ofneutrino communication technologies and devices through whichinformation (including binary information) is transmitted using a beamof neutrinos.

The communications resources 310 can also include mechanisms foraccessing storage resources 308 within the storage system 306 utilizingserial attached SCSI (‘SAS’), serial ATA (‘SATA’) bus interfaces forconnecting storage resources 308 within the storage system 306 to hostbus adapters within the storage system 306, internet small computersystems interface (‘iSCSI’) technologies to provide block-level accessto storage resources 308 within the storage system 306, and othercommunications resources that that may be useful in facilitating datacommunications between components within the storage system 306, as wellas data communications between the storage system 306 and computingdevices that are outside of the storage system 306.

The storage system 306 depicted in FIG. 3B also includes processingresources 312 that may be useful in useful in executing computer programinstructions and performing other computational tasks within the storagesystem 306. The processing resources 312 may include one or more ASICsthat are customized for some particular purpose as well as one or moreCPUs. The processing resources 312 may also include one or more DSPs,one or more FPGAs, one or more systems on a chip (‘SoCs’), or other formof processing resources 312. The storage system 306 may utilize thestorage resources 312 to perform a variety of tasks including, but notlimited to, supporting the execution of software resources 314 that willbe described in greater detail below.

The storage system 306 depicted in FIG. 3B also includes softwareresources 314 that, when executed by processing resources 312 within thestorage system 306, may perform a vast array of tasks. The softwareresources 314 may include, for example, one or more modules of computerprogram instructions that when executed by processing resources 312within the storage system 306 are useful in carrying out various dataprotection techniques to preserve the integrity of data that is storedwithin the storage systems. Readers will appreciate that such dataprotection techniques may be carried out, for example, by systemsoftware executing on computer hardware within the storage system, by acloud services provider, or in other ways. Such data protectiontechniques can include, for example, data archiving techniques thatcause data that is no longer actively used to be moved to a separatestorage device or separate storage system for long-term retention, databackup techniques through which data stored in the storage system may becopied and stored in a distinct location to avoid data loss in the eventof equipment failure or some other form of catastrophe with the storagesystem, data replication techniques through which data stored in thestorage system is replicated to another storage system such that thedata may be accessible via multiple storage systems, data snapshottingtechniques through which the state of data within the storage system iscaptured at various points in time, data and database cloning techniquesthrough which duplicate copies of data and databases may be created, andother data protection techniques.

The software resources 314 may also include software that is useful inimplementing software-defined storage (‘SDS’). In such an example, thesoftware resources 314 may include one or more modules of computerprogram instructions that, when executed, are useful in policy-basedprovisioning and management of data storage that is independent of theunderlying hardware. Such software resources 314 may be useful inimplementing storage virtualization to separate the storage hardwarefrom the software that manages the storage hardware.

The software resources 314 may also include software that is useful infacilitating and optimizing I/O operations that are directed to thestorage resources 308 in the storage system 306. For example, thesoftware resources 314 may include software modules that perform carryout various data reduction techniques such as, for example, datacompression, data deduplication, and others. The software resources 314may include software modules that intelligently group together I/Ooperations to facilitate better usage of the underlying storage resource308, software modules that perform data migration operations to migratefrom within a storage system, as well as software modules that performother functions. Such software resources 314 may be embodied as one ormore software containers or in many other ways.

For further explanation, FIG. 3C sets forth an example of a cloud-basedstorage system 318 in accordance with some embodiments of the presentdisclosure. In the example depicted in FIG. 3C, the cloud-based storagesystem 318 is created entirely in a cloud computing environment 316 suchas, for example, Amazon Web Services (‘AWS’), Microsoft Azure, GoogleCloud Platform, IBM Cloud, Oracle Cloud, and others. The cloud-basedstorage system 318 may be used to provide services similar to theservices that may be provided by the storage systems described above.For example, the cloud-based storage system 318 may be used to provideblock storage services to users of the cloud-based storage system 318,the cloud-based storage system 318 may be used to provide storageservices to users of the cloud-based storage system 318 through the useof solid-state storage, and so on.

The cloud-based storage system 318 depicted in FIG. 3C includes twocloud computing instances 320, 322 that each are used to support theexecution of a storage controller application 324, 326. The cloudcomputing instances 320, 322 may be embodied, for example, as instancesof cloud computing resources (e.g., virtual machines) that may beprovided by the cloud computing environment 316 to support the executionof software applications such as the storage controller application 324,326. In one embodiment, the cloud computing instances 320, 322 may beembodied as Amazon Elastic Compute Cloud (‘EC2’) instances. In such anexample, an Amazon Machine Image (‘AMI’) that includes the storagecontroller application 324, 326 may be booted to create and configure avirtual machine that may execute the storage controller application 324,326.

In the example method depicted in FIG. 3C, the storage controllerapplication 324, 326 may be embodied as a module of computer programinstructions that, when executed, carries out various storage tasks. Forexample, the storage controller application 324, 326 may be embodied asa module of computer program instructions that, when executed, carriesout the same tasks as the controllers 110A, 1108 in FIG. 1A describedabove such as writing data received from the users of the cloud-basedstorage system 318 to the cloud-based storage system 318, erasing datafrom the cloud-based storage system 318, retrieving data from thecloud-based storage system 318 and providing such data to users of thecloud-based storage system 318, monitoring and reporting of diskutilization and performance, performing redundancy operations, such asRAID or RAID-like data redundancy operations, compressing data,encrypting data, deduplicating data, and so forth. Readers willappreciate that because there are two cloud computing instances 320, 322that each include the storage controller application 324, 326, in someembodiments one cloud computing instance 320 may operate as the primarycontroller as described above while the other cloud computing instance322 may operate as the secondary controller as described above. Readerswill appreciate that the storage controller application 324, 326depicted in FIG. 3C may include identical source code that is executedwithin different cloud computing instances 320, 322.

Consider an example in which the cloud computing environment 316 isembodied as AWS and the cloud computing instances are embodied as EC2instances. In such an example, the cloud computing instance 320 thatoperates as the primary controller may be deployed on one of theinstance types that has a relatively large amount of memory andprocessing power while the cloud computing instance 322 that operates asthe secondary controller may be deployed on one of the instance typesthat has a relatively small amount of memory and processing power. Insuch an example, upon the occurrence of a failover event where the rolesof primary and secondary are switched, a double failover may actually becarried out such that: 1) a first failover event where the cloudcomputing instance 322 that formerly operated as the secondarycontroller begins to operate as the primary controller, and 2) a thirdcloud computing instance (not shown) that is of an instance type thathas a relatively large amount of memory and processing power is spun upwith a copy of the storage controller application, where the third cloudcomputing instance begins operating as the primary controller while thecloud computing instance 322 that originally operated as the secondarycontroller begins operating as the secondary controller again. In suchan example, the cloud computing instance 320 that formerly operated asthe primary controller may be terminated. Readers will appreciate thatin alternative embodiments, the cloud computing instance 320 that isoperating as the secondary controller after the failover event maycontinue to operate as the secondary controller and the cloud computinginstance 322 that operated as the primary controller after theoccurrence of the failover event may be terminated once the primary rolehas been assumed by the third cloud computing instance (not shown).

Readers will appreciate that while the embodiments described aboverelate to embodiments where one cloud computing instance 320 operates asthe primary controller and the second cloud computing instance 322operates as the secondary controller, other embodiments are within thescope of the present disclosure. For example, each cloud computinginstance 320, 322 may operate as a primary controller for some portionof the address space supported by the cloud-based storage system 318,each cloud computing instance 320, 322 may operate as a primarycontroller where the servicing of I/O operations directed to thecloud-based storage system 318 are divided in some other way, and so on.In fact, in other embodiments where costs savings may be prioritizedover performance demands, only a single cloud computing instance mayexist that contains the storage controller application.

The cloud-based storage system 318 depicted in FIG. 3C includes cloudcomputing instances 340 a, 340 b, 340 n with local storage 330, 334,338. The cloud computing instances 340 a, 340 b, 340 n depicted in FIG.3C may be embodied, for example, as instances of cloud computingresources that may be provided by the cloud computing environment 316 tosupport the execution of software applications. The cloud computinginstances 340 a, 340 b, 340 n of FIG. 3C may differ from the cloudcomputing instances 320, 322 described above as the cloud computinginstances 340 a, 340 b, 340 n of FIG. 3C have local storage 330, 334,338 resources whereas the cloud computing instances 320, 322 thatsupport the execution of the storage controller application 324, 326need not have local storage resources. The cloud computing instances 340a, 340 b, 340 n with local storage 330, 334, 338 may be embodied, forexample, as EC2 M5 instances that include one or more SSDs, as EC2 R5instances that include one or more SSDs, as EC2 I3 instances thatinclude one or more SSDs, and so on. In some embodiments, the localstorage 330, 334, 338 must be embodied as solid-state storage (e.g.,SSDs) rather than storage that makes use of hard disk drives.

In the example depicted in FIG. 3C, each of the cloud computinginstances 340 a, 340 b, 340 n with local storage 330, 334, 338 caninclude a software daemon 328, 332, 336 that, when executed by a cloudcomputing instance 340 a, 340 b, 340 n can present itself to the storagecontroller applications 324, 326 as if the cloud computing instance 340a, 340 b, 340 n were a physical storage device (e.g., one or more SSDs).In such an example, the software daemon 328, 332, 336 may includecomputer program instructions similar to those that would normally becontained on a storage device such that the storage controllerapplications 324, 326 can send and receive the same commands that astorage controller would send to storage devices. In such a way, thestorage controller applications 324, 326 may include code that isidentical to (or substantially identical to) the code that would beexecuted by the controllers in the storage systems described above. Inthese and similar embodiments, communications between the storagecontroller applications 324, 326 and the cloud computing instances 340a, 340 b, 340 n with local storage 330, 334, 338 may utilize iSCSI, NVMeover TCP, messaging, a custom protocol, or in some other mechanism.

In the example depicted in FIG. 3C, each of the cloud computinginstances 340 a, 340 b, 340 n with local storage 330, 334, 338 may alsobe coupled to block-storage 342, 344, 346 that is offered by the cloudcomputing environment 316. The block-storage 342, 344, 346 that isoffered by the cloud computing environment 316 may be embodied, forexample, as Amazon Elastic Block Store (‘EBS’) volumes. For example, afirst EBS volume may be coupled to a first cloud computing instance 340a, a second EBS volume may be coupled to a second cloud computinginstance 340 b, and a third EBS volume may be coupled to a third cloudcomputing instance 340 n. In such an example, the block-storage 342,344, 346 that is offered by the cloud computing environment 316 may beutilized in a manner that is similar to how the NVRAM devices describedabove are utilized, as the software daemon 328, 332, 336 (or some othermodule) that is executing within a particular cloud comping instance 340a, 340 b, 340 n may, upon receiving a request to write data, initiate awrite of the data to its attached EBS volume as well as a write of thedata to its local storage 330, 334, 338 resources. In some alternativeembodiments, data may only be written to the local storage 330, 334, 338resources within a particular cloud comping instance 340 a, 340 b, 340n. In an alternative embodiment, rather than using the block-storage342, 344, 346 that is offered by the cloud computing environment 316 asNVRAM, actual RAM on each of the cloud computing instances 340 a, 340 b,340 n with local storage 330, 334, 338 may be used as NVRAM, therebydecreasing network utilization costs that would be associated with usingan EBS volume as the NVRAM.

In the example depicted in FIG. 3C, the cloud computing instances 340 a,340 b, 340 n with local storage 330, 334, 338 may be utilized, by cloudcomputing instances 320, 322 that support the execution of the storagecontroller application 324, 326 to service I/O operations that aredirected to the cloud-based storage system 318. Consider an example inwhich a first cloud computing instance 320 that is executing the storagecontroller application 324 is operating as the primary controller. Insuch an example, the first cloud computing instance 320 that isexecuting the storage controller application 324 may receive (directlyor indirectly via the secondary controller) requests to write data tothe cloud-based storage system 318 from users of the cloud-based storagesystem 318. In such an example, the first cloud computing instance 320that is executing the storage controller application 324 may performvarious tasks such as, for example, deduplicating the data contained inthe request, compressing the data contained in the request, determiningwhere to the write the data contained in the request, and so on, beforeultimately sending a request to write a deduplicated, encrypted, orotherwise possibly updated version of the data to one or more of thecloud computing instances 340 a, 340 b, 340 n with local storage 330,334, 338. Either cloud computing instance 320, 322, in some embodiments,may receive a request to read data from the cloud-based storage system318 and may ultimately send a request to read data to one or more of thecloud computing instances 340 a, 340 b, 340 n with local storage 330,334, 338.

Readers will appreciate that when a request to write data is received bya particular cloud computing instance 340 a, 340 b, 340 n with localstorage 330, 334, 338, the software daemon 328, 332, 336 or some othermodule of computer program instructions that is executing on theparticular cloud computing instance 340 a, 340 b, 340 n may beconfigured to not only write the data to its own local storage 330, 334,338 resources and any appropriate block-storage 342, 344, 346 that areoffered by the cloud computing environment 316, but the software daemon328, 332, 336 or some other module of computer program instructions thatis executing on the particular cloud computing instance 340 a, 340 b,340 n may also be configured to write the data to cloud-based objectstorage 348 that is attached to the particular cloud computing instance340 a, 340 b, 340 n. The cloud-based object storage 348 that is attachedto the particular cloud computing instance 340 a, 340 b, 340 n may beembodied, for example, as Amazon Simple Storage Service (‘S3’) storagethat is accessible by the particular cloud computing instance 340 a, 340b, 340 n. In other embodiments, the cloud computing instances 320, 322that each include the storage controller application 324, 326 mayinitiate the storage of the data in the local storage 330, 334, 338 ofthe cloud computing instances 340 a, 340 b, 340 n and the cloud-basedobject storage 348.

Readers will appreciate that, as described above, the cloud-basedstorage system 318 may be used to provide block storage services tousers of the cloud-based storage system 318. While the local storage330, 334, 338 resources and the block-storage 342, 344, 346 resourcesthat are utilized by the cloud computing instances 340 a, 340 b, 340 nmay support block-level access, the cloud-based object storage 348 thatis attached to the particular cloud computing instance 340 a, 340 b, 340n supports only object-based access. In order to address this, thesoftware daemon 328, 332, 336 or some other module of computer programinstructions that is executing on the particular cloud computinginstance 340 a, 340 b, 340 n may be configured to take blocks of data,package those blocks into objects, and write the objects to thecloud-based object storage 348 that is attached to the particular cloudcomputing instance 340 a, 340 b, 340 n.

Consider an example in which data is written to the local storage 330,334, 338 resources and the block-storage 342, 344, 346 resources thatare utilized by the cloud computing instances 340 a, 340 b, 340 n in 1MB blocks. In such an example, assume that a user of the cloud-basedstorage system 318 issues a request to write data that, after beingcompressed and deduplicated by the storage controller application 324,326 results in the need to write 5 MB of data. In such an example,writing the data to the local storage 330, 334, 338 resources and theblock-storage 342, 344, 346 resources that are utilized by the cloudcomputing instances 340 a, 340 b, 340 n is relatively straightforward as5 blocks that are 1 MB in size are written to the local storage 330,334, 338 resources and the block-storage 342, 344, 346 resources thatare utilized by the cloud computing instances 340 a, 340 b, 340 n. Insuch an example, the software daemon 328, 332, 336 or some other moduleof computer program instructions that is executing on the particularcloud computing instance 340 a, 340 b, 340 n may be configured to: 1)create a first object that includes the first 1 MB of data and write thefirst object to the cloud-based object storage 348, 2) create a secondobject that includes the second 1 MB of data and write the second objectto the cloud-based object storage 348, 3) create a third object thatincludes the third 1 MB of data and write the third object to thecloud-based object storage 348, and so on. As such, in some embodiments,each object that is written to the cloud-based object storage 348 may beidentical (or nearly identical) in size. Readers will appreciate that insuch an example, metadata that is associated with the data itself may beincluded in each object (e.g., the first 1 MB of the object is data andthe remaining portion is metadata associated with the data).

Readers will appreciate that the cloud-based object storage 348 may beincorporated into the cloud-based storage system 318 to increase thedurability of the cloud-based storage system 318. Continuing with theexample described above where the cloud computing instances 340 a, 340b, 340 n are EC2 instances, readers will understand that EC2 instancesare only guaranteed to have a monthly uptime of 99.9% and data stored inthe local instance store only persists during the lifetime of the EC2instance. As such, relying on the cloud computing instances 340 a, 340b, 340 n with local storage 330, 334, 338 as the only source ofpersistent data storage in the cloud-based storage system 318 may resultin a relatively unreliable storage system. Likewise, EBS volumes aredesigned for 99.999% availability. As such, even relying on EBS as thepersistent data store in the cloud-based storage system 318 may resultin a storage system that is not sufficiently durable. Amazon S3,however, is designed to provide 99.999999999% durability, meaning that acloud-based storage system 318 that can incorporate S3 into its pool ofstorage is substantially more durable than various other options.

Readers will appreciate that while a cloud-based storage system 318 thatcan incorporate S3 into its pool of storage is substantially moredurable than various other options, utilizing S3 as the primary pool ofstorage may result in storage system that has relatively slow responsetimes and relatively long I/O latencies. As such, the cloud-basedstorage system 318 depicted in FIG. 3C not only stores data in S3 butthe cloud-based storage system 318 also stores data in local storage330, 334, 338 resources and block-storage 342, 344, 346 resources thatare utilized by the cloud computing instances 340 a, 340 b, 340 n, suchthat read operations can be serviced from local storage 330, 334, 338resources and the block-storage 342, 344, 346 resources that areutilized by the cloud computing instances 340 a, 340 b, 340 n, therebyreducing read latency when users of the cloud-based storage system 318attempt to read data from the cloud-based storage system 318.

In some embodiments, all data that is stored by the cloud-based storagesystem 318 may be stored in both: 1) the cloud-based object storage 348,and 2) at least one of the local storage 330, 334, 338 resources orblock-storage 342, 344, 346 resources that are utilized by the cloudcomputing instances 340 a, 340 b, 340 n. In such embodiments, the localstorage 330, 334, 338 resources and block-storage 342, 344, 346resources that are utilized by the cloud computing instances 340 a, 340b, 340 n may effectively operate as cache that generally includes alldata that is also stored in S3, such that all reads of data may beserviced by the cloud computing instances 340 a, 340 b, 340 n withoutrequiring the cloud computing instances 340 a, 340 b, 340 n to accessthe cloud-based object storage 348. Readers will appreciate that inother embodiments, however, all data that is stored by the cloud-basedstorage system 318 may be stored in the cloud-based object storage 348,but less than all data that is stored by the cloud-based storage system318 may be stored in at least one of the local storage 330, 334, 338resources or block-storage 342, 344, 346 resources that are utilized bythe cloud computing instances 340 a, 340 b, 340 n. In such an example,various policies may be utilized to determine which subset of the datathat is stored by the cloud-based storage system 318 should reside inboth: 1) the cloud-based object storage 348, and 2) at least one of thelocal storage 330, 334, 338 resources or block-storage 342, 344, 346resources that are utilized by the cloud computing instances 340 a, 340b, 340 n.

As described above, when the cloud computing instances 340 a, 340 b, 340n with local storage 330, 334, 338 are embodied as EC2 instances, thecloud computing instances 340 a, 340 b, 340 n with local storage 330,334, 338 are only guaranteed to have a monthly uptime of 99.9% and datastored in the local instance store only persists during the lifetime ofeach cloud computing instance 340 a, 340 b, 340 n with local storage330, 334, 338. As such, one or more modules of computer programinstructions that are executing within the cloud-based storage system318 (e.g., a monitoring module that is executing on its own EC2instance) may be designed to handle the failure of one or more of thecloud computing instances 340 a, 340 b, 340 n with local storage 330,334, 338. In such an example, the monitoring module may handle thefailure of one or more of the cloud computing instances 340 a, 340 b,340 n with local storage 330, 334, 338 by creating one or more new cloudcomputing instances with local storage, retrieving data that was storedon the failed cloud computing instances 340 a, 340 b, 340 n from thecloud-based object storage 348, and storing the data retrieved from thecloud-based object storage 348 in local storage on the newly createdcloud computing instances. Readers will appreciate that many variants ofthis process may be implemented.

Consider an example in which all cloud computing instances 340 a, 340 b,340 n with local storage 330, 334, 338 failed. In such an example, themonitoring module may create new cloud computing instances with localstorage, where high-bandwidth instances types are selected that allowfor the maximum data transfer rates between the newly createdhigh-bandwidth cloud computing instances with local storage and thecloud-based object storage 348. Readers will appreciate that instancestypes are selected that allow for the maximum data transfer ratesbetween the new cloud computing instances and the cloud-based objectstorage 348 such that the new high-bandwidth cloud computing instancescan be rehydrated with data from the cloud-based object storage 348 asquickly as possible. Once the new high-bandwidth cloud computinginstances are rehydrated with data from the cloud-based object storage348, less expensive lower-bandwidth cloud computing instances may becreated, data may be migrated to the less expensive lower-bandwidthcloud computing instances, and the high-bandwidth cloud computinginstances may be terminated.

Readers will appreciate that in some embodiments, the number of newcloud computing instances that are created may substantially exceed thenumber of cloud computing instances that are needed to locally store allof the data stored by the cloud-based storage system 318. The number ofnew cloud computing instances that are created may substantially exceedthe number of cloud computing instances that are needed to locally storeall of the data stored by the cloud-based storage system 318 in order tomore rapidly pull data from the cloud-based object storage 348 and intothe new cloud computing instances, as each new cloud computing instancecan (in parallel) retrieve some portion of the data stored by thecloud-based storage system 318. In such embodiments, once the datastored by the cloud-based storage system 318 has been pulled into thenewly created cloud computing instances, the data may be consolidatedwithin a subset of the newly created cloud computing instances and thosenewly created cloud computing instances that are excessive may beterminated.

Consider an example in which 1000 cloud computing instances are neededin order to locally store all valid data that users of the cloud-basedstorage system 318 have written to the cloud-based storage system 318.In such an example, assume that all 1,000 cloud computing instancesfail. In such an example, the monitoring module may cause 100,000 cloudcomputing instances to be created, where each cloud computing instanceis responsible for retrieving, from the cloud-based object storage 348,distinct 1/100,000th chunks of the valid data that users of thecloud-based storage system 318 have written to the cloud-based storagesystem 318 and locally storing the distinct chunk of the dataset that itretrieved. In such an example, because each of the 100,000 cloudcomputing instances can retrieve data from the cloud-based objectstorage 348 in parallel, the caching layer may be restored 100 timesfaster as compared to an embodiment where the monitoring module onlycreate 1000 replacement cloud computing instances. In such an example,over time the data that is stored locally in the 100,000 could beconsolidated into 1,000 cloud computing instances and the remaining99,000 cloud computing instances could be terminated.

Readers will appreciate that various performance aspects of thecloud-based storage system 318 may be monitored (e.g., by a monitoringmodule that is executing in an EC2 instance) such that the cloud-basedstorage system 318 can be scaled-up or scaled-out as needed. Consider anexample in which the monitoring module monitors the performance of thecould-based storage system 318 via communications with one or more ofthe cloud computing instances 320, 322 that each are used to support theexecution of a storage controller application 324, 326, via monitoringcommunications between cloud computing instances 320, 322, 340 a, 340 b,340 n, via monitoring communications between cloud computing instances320, 322, 340 a, 340 b, 340 n and the cloud-based object storage 348, orin some other way. In such an example, assume that the monitoring moduledetermines that the cloud computing instances 320, 322 that are used tosupport the execution of a storage controller application 324, 326 areundersized and not sufficiently servicing the I/O requests that areissued by users of the cloud-based storage system 318. In such anexample, the monitoring module may create a new, more powerful cloudcomputing instance (e.g., a cloud computing instance of a type thatincludes more processing power, more memory, etc. . . . ) that includesthe storage controller application such that the new, more powerfulcloud computing instance can begin operating as the primary controller.Likewise, if the monitoring module determines that the cloud computinginstances 320, 322 that are used to support the execution of a storagecontroller application 324, 326 are oversized and that cost savingscould be gained by switching to a smaller, less powerful cloud computinginstance, the monitoring module may create a new, less powerful (andless expensive) cloud computing instance that includes the storagecontroller application such that the new, less powerful cloud computinginstance can begin operating as the primary controller.

Consider, as an additional example of dynamically sizing the cloud-basedstorage system 318, an example in which the monitoring module determinesthat the utilization of the local storage that is collectively providedby the cloud computing instances 340 a, 340 b, 340 n has reached apredetermined utilization threshold (e.g., 95%). In such an example, themonitoring module may create additional cloud computing instances withlocal storage to expand the pool of local storage that is offered by thecloud computing instances. Alternatively, the monitoring module maycreate one or more new cloud computing instances that have largeramounts of local storage than the already existing cloud computinginstances 340 a, 340 b, 340 n, such that data stored in an alreadyexisting cloud computing instance 340 a, 340 b, 340 n can be migrated tothe one or more new cloud computing instances and the already existingcloud computing instance 340 a, 340 b, 340 n can be terminated, therebyexpanding the pool of local storage that is offered by the cloudcomputing instances. Likewise, if the pool of local storage that isoffered by the cloud computing instances is unnecessarily large, datacan be consolidated and some cloud computing instances can beterminated.

Readers will appreciate that the cloud-based storage system 318 may besized up and down automatically by a monitoring module applying apredetermined set of rules that may be relatively simple of relativelycomplicated. In fact, the monitoring module may not only take intoaccount the current state of the cloud-based storage system 318, but themonitoring module may also apply predictive policies that are based on,for example, observed behavior (e.g., every night from 10 PM until 6 AMusage of the storage system is relatively light), predeterminedfingerprints (e.g., every time a virtual desktop infrastructure adds 100virtual desktops, the number of IOPS directed to the storage systemincrease by X), and so on. In such an example, the dynamic scaling ofthe cloud-based storage system 318 may be based on current performancemetrics, predicted workloads, and many other factors, includingcombinations thereof.

Readers will further appreciate that because the cloud-based storagesystem 318 may be dynamically scaled, the cloud-based storage system 318may even operate in a way that is more dynamic. Consider the example ofgarbage collection. In a traditional storage system, the amount ofstorage is fixed. As such, at some point the storage system may beforced to perform garbage collection as the amount of available storagehas become so constrained that the storage system is on the verge ofrunning out of storage. In contrast, the cloud-based storage system 318described here can always ‘add’ additional storage (e.g., by adding morecloud computing instances with local storage). Because the cloud-basedstorage system 318 described here can always ‘add’ additional storage,the cloud-based storage system 318 can make more intelligent decisionsregarding when to perform garbage collection. For example, thecloud-based storage system 318 may implement a policy that garbagecollection only be performed when the number of IOPS being serviced bythe cloud-based storage system 318 falls below a certain level. In someembodiments, other system-level functions (e.g., deduplication,compression) may also be turned off and on in response to system load,given that the size of the cloud-based storage system 318 is notconstrained in the same way that traditional storage systems areconstrained.

Readers will appreciate that embodiments of the present disclosureresolve an issue with block-storage services offered by some cloudcomputing environments as some cloud computing environments only allowfor one cloud computing instance to connect to a block-storage volume ata single time. For example, in Amazon AWS, only a single EC2 instancemay be connected to an EBS volume. Through the use of EC2 instances withlocal storage, embodiments of the present disclosure can offermulti-connect capabilities where multiple EC2 instances can connect toanother EC2 instance with local storage (‘a drive instance’). In suchembodiments, the drive instances may include software executing withinthe drive instance that allows the drive instance to support I/Odirected to a particular volume from each connected EC2 instance. Assuch, some embodiments of the present disclosure may be embodied asmulti-connect block storage services that may not include all of thecomponents depicted in FIG. 3C.

In some embodiments, especially in embodiments where the cloud-basedobject storage 348 resources are embodied as Amazon S3, the cloud-basedstorage system 318 may include one or more modules (e.g., a module ofcomputer program instructions executing on an EC2 instance) that areconfigured to ensure that when the local storage of a particular cloudcomputing instance is rehydrated with data from S3, the appropriate datais actually in S3. This issue arises largely because S3 implements aneventual consistency model where, when overwriting an existing object,reads of the object will eventually (but not necessarily immediately)become consistent and will eventually (but not necessarily immediately)return the overwritten version of the object. To address this issue, insome embodiments of the present disclosure, objects in S3 are neveroverwritten. Instead, a traditional ‘overwrite’ would result in thecreation of the new object (that includes the updated version of thedata) and the eventual deletion of the old object (that includes theprevious version of the data).

In some embodiments of the present disclosure, as part of an attempt tonever (or almost never) overwrite an object, when data is written to S3the resultant object may be tagged with a sequence number. In someembodiments, these sequence numbers may be persisted elsewhere (e.g., ina database) such that at any point in time, the sequence numberassociated with the most up-to-date version of some piece of data can beknown. In such a way, a determination can be made as to whether S3 hasthe most recent version of some piece of data by merely reading thesequence number associated with an object—and without actually readingthe data from S3. The ability to make this determination may beparticularly important when a cloud computing instance with localstorage crashes, as it would be undesirable to rehydrate the localstorage of a replacement cloud computing instance with out-of-date data.In fact, because the cloud-based storage system 318 does not need toaccess the data to verify its validity, the data can stay encrypted andaccess charges can be avoided.

The storage systems described above may carry out intelligent databackup techniques through which data stored in the storage system may becopied and stored in a distinct location to avoid data loss in the eventof equipment failure or some other form of catastrophe. For example, thestorage systems described above may be configured to examine each backupto avoid restoring the storage system to an undesirable state. Consideran example in which malware infects the storage system. In such anexample, the storage system may include software resources 314 that canscan each backup to identify backups that were captured before themalware infected the storage system and those backups that were capturedafter the malware infected the storage system. In such an example, thestorage system may restore itself from a backup that does not includethe malware—or at least not restore the portions of a backup thatcontained the malware. In such an example, the storage system mayinclude software resources 314 that can scan each backup to identify thepresences of malware (or a virus, or some other undesirable), forexample, by identifying write operations that were serviced by thestorage system and originated from a network subnet that is suspected tohave delivered the malware, by identifying write operations that wereserviced by the storage system and originated from a user that issuspected to have delivered the malware, by identifying write operationsthat were serviced by the storage system and examining the content ofthe write operation against fingerprints of the malware, and in manyother ways.

Readers will further appreciate that the backups (often in the form ofone or more snapshots) may also be utilized to perform rapid recovery ofthe storage system. Consider an example in which the storage system isinfected with ransomware that locks users out of the storage system. Insuch an example, software resources 314 within the storage system may beconfigured to detect the presence of ransomware and may be furtherconfigured to restore the storage system to a point-in-time, using theretained backups, prior to the point-in-time at which the ransomwareinfected the storage system. In such an example, the presence ofransomware may be explicitly detected through the use of software toolsutilized by the system, through the use of a key (e.g., a USB drive)that is inserted into the storage system, or in a similar way. Likewise,the presence of ransomware may be inferred in response to systemactivity meeting a predetermined fingerprint such as, for example, noreads or writes coming into the system for a predetermined period oftime.

Readers will appreciate that the various components described above maybe grouped into one or more optimized computing packages as convergedinfrastructures. Such converged infrastructures may include pools ofcomputers, storage and networking resources that can be shared bymultiple applications and managed in a collective manner usingpolicy-driven processes. Such converged infrastructures may beimplemented with a converged infrastructure reference architecture, withstandalone appliances, with a software driven hyper-converged approach(e.g., hyper-converged infrastructures), or in other ways.

Readers will appreciate that the storage systems described above may beuseful for supporting various types of software applications. Forexample, the storage system 306 may be useful in supporting artificialintelligence (‘AI’) applications, database applications, DevOpsprojects, electronic design automation tools, event-driven softwareapplications, high performance computing applications, simulationapplications, high-speed data capture and analysis applications, machinelearning applications, media production applications, media servingapplications, picture archiving and communication systems (‘PACS’)applications, software development applications, virtual realityapplications, augmented reality applications, and many other types ofapplications by providing storage resources to such applications.

The storage systems described above may operate to support a widevariety of applications. In view of the fact that the storage systemsinclude compute resources, storage resources, and a wide variety ofother resources, the storage systems may be well suited to supportapplications that are resource intensive such as, for example, AIapplications. AI applications may be deployed in a variety of fields,including: predictive maintenance in manufacturing and related fields,healthcare applications such as patient data & risk analytics, retailand marketing deployments (e.g., search advertising, social mediaadvertising), supply chains solutions, fintech solutions such asbusiness analytics & reporting tools, operational deployments such asreal-time analytics tools, application performance management tools, ITinfrastructure management tools, and many others.

Such AI applications may enable devices to perceive their environmentand take actions that maximize their chance of success at some goal.Examples of such AI applications can include IBM Watson, MicrosoftOxford, Google DeepMind, Baidu Minwa, and others. The storage systemsdescribed above may also be well suited to support other types ofapplications that are resource intensive such as, for example, machinelearning applications. Machine learning applications may perform varioustypes of data analysis to automate analytical model building. Usingalgorithms that iteratively learn from data, machine learningapplications can enable computers to learn without being explicitlyprogrammed. One particular area of machine learning is referred to asreinforcement learning, which involves taking suitable actions tomaximize reward in a particular situation. Reinforcement learning may beemployed to find the best possible behavior or path that a particularsoftware application or machine should take in a specific situation.Reinforcement learning differs from other areas of machine learning(e.g., supervised learning, unsupervised learning) in that correctinput/output pairs need not be presented for reinforcement learning andsub-optimal actions need not be explicitly corrected.

In addition to the resources already described, the storage systemsdescribed above may also include graphics processing units (‘GPUs’),occasionally referred to as visual processing unit (‘VPUs’). Such GPUsmay be embodied as specialized electronic circuits that rapidlymanipulate and alter memory to accelerate the creation of images in aframe buffer intended for output to a display device. Such GPUs may beincluded within any of the computing devices that are part of thestorage systems described above, including as one of many individuallyscalable components of a storage system, where other examples ofindividually scalable components of such storage system can includestorage components, memory components, compute components (e.g., CPUs,FPGAs, ASICs), networking components, software components, and others.In addition to GPUs, the storage systems described above may alsoinclude neural network processors (‘NNPs’) for use in various aspects ofneural network processing. Such NNPs may be used in place of (or inaddition to) GPUs and may be also be independently scalable.

As described above, the storage systems described herein may beconfigured to support artificial intelligence applications, machinelearning applications, big data analytics applications, and many othertypes of applications. The rapid growth in these sort of applications isbeing driven by three technologies: deep learning (DL), GPU processors,and Big Data. Deep learning is a computing model that makes use ofmassively parallel neural networks inspired by the human brain. Insteadof experts handcrafting software, a deep learning model writes its ownsoftware by learning from lots of examples. Such GPUs may includethousands of cores that are well-suited to run algorithms that looselyrepresent the parallel nature of the human brain.

Advances in deep neural networks have ignited a new wave of algorithmsand tools for data scientists to tap into their data with artificialintelligence (AI). With improved algorithms, larger data sets, andvarious frameworks (including open-source software libraries for machinelearning across a range of tasks), data scientists are tackling new usecases like autonomous driving vehicles, natural language processing andunderstanding, computer vision, machine reasoning, strong AI, and manyothers. Applications of such techniques may include: machine andvehicular object detection, identification and avoidance; visualrecognition, classification and tagging; algorithmic financial tradingstrategy performance management; simultaneous localization and mapping;predictive maintenance of high-value machinery; prevention against cybersecurity threats, expertise automation; image recognition andclassification; question answering; robotics; text analytics(extraction, classification) and text generation and translation; andmany others. Applications of AI techniques has materialized in a widearray of products include, for example, Amazon Echo's speech recognitiontechnology that allows users to talk to their machines, GoogleTranslate™ which allows for machine-based language translation,Spotify's Discover Weekly that provides recommendations on new songs andartists that a user may like based on the user's usage and trafficanalysis, Quill's text generation offering that takes structured dataand turns it into narrative stories, Chatbots that provide real-time,contextually specific answers to questions in a dialog format, and manyothers.

Data is the heart of modern AI and deep learning algorithms. Beforetraining can begin, one problem that must be addressed revolves aroundcollecting the labeled data that is crucial for training an accurate AImodel. A full scale AI deployment may be required to continuouslycollect, clean, transform, label, and store large amounts of data.Adding additional high quality data points directly translates to moreaccurate models and better insights. Data samples may undergo a seriesof processing steps including, but not limited to: 1) ingesting the datafrom an external source into the training system and storing the data inraw form, 2) cleaning and transforming the data in a format convenientfor training, including linking data samples to the appropriate label,3) exploring parameters and models, quickly testing with a smallerdataset, and iterating to converge on the most promising models to pushinto the production cluster, 4) executing training phases to selectrandom batches of input data, including both new and older samples, andfeeding those into production GPU servers for computation to updatemodel parameters, and 5) evaluating including using a holdback portionof the data not used in training in order to evaluate model accuracy onthe holdout data. This lifecycle may apply for any type of parallelizedmachine learning, not just neural networks or deep learning. Forexample, standard machine learning frameworks may rely on CPUs insteadof GPUs but the data ingest and training workflows may be the same.Readers will appreciate that a single shared storage data hub creates acoordination point throughout the lifecycle without the need for extradata copies among the ingest, preprocessing, and training stages. Rarelyis the ingested data used for only one purpose, and shared storage givesthe flexibility to train multiple different models or apply traditionalanalytics to the data.

Readers will appreciate that each stage in the AI data pipeline may havevarying requirements from the data hub (e.g., the storage system orcollection of storage systems). Scale-out storage systems must deliveruncompromising performance for all manner of access types andpatterns—from small, metadata-heavy to large files, from random tosequential access patterns, and from low to high concurrency. Thestorage systems described above may serve as an ideal AI data hub as thesystems may service unstructured workloads. In the first stage, data isideally ingested and stored on to the same data hub that followingstages will use, in order to avoid excess data copying. The next twosteps can be done on a standard compute server that optionally includesa GPU, and then in the fourth and last stage, full training productionjobs are run on powerful GPU-accelerated servers. Often, there is aproduction pipeline alongside an experimental pipeline operating on thesame dataset. Further, the GPU-accelerated servers can be usedindependently for different models or joined together to train on onelarger model, even spanning multiple systems for distributed training.If the shared storage tier is slow, then data must be copied to localstorage for each phase, resulting in wasted time staging data ontodifferent servers. The ideal data hub for the AI training pipelinedelivers performance similar to data stored locally on the server nodewhile also having the simplicity and performance to enable all pipelinestages to operate concurrently.

Although the preceding paragraphs discuss deep learning applications,readers will appreciate that the storage systems described herein mayalso be part of a distributed deep learning (‘DDL’) platform to supportthe execution of DDL algorithms. The storage systems described above mayalso be paired with other technologies such as TensorFlow, anopen-source software library for dataflow programming across a range oftasks that may be used for machine learning applications such as neuralnetworks, to facilitate the development of such machine learning models,applications, and so on.

The storage systems described above may also be used in a neuromorphiccomputing environment. Neuromorphic computing is a form of computingthat mimics brain cells. To support neuromorphic computing, anarchitecture of interconnected “neurons” replace traditional computingmodels with low-powered signals that go directly between neurons formore efficient computation. Neuromorphic computing may make use ofvery-large-scale integration (VLSI) systems containing electronic analogcircuits to mimic neuro-biological architectures present in the nervoussystem, as well as analog, digital, mixed-mode analog/digital VLSI, andsoftware systems that implement models of neural systems for perception,motor control, or multisensory integration.

Readers will appreciate that the storage systems described above may beconfigured to support the storage or use of (among other types of data)blockchains. In addition to supporting the storage and use of blockchaintechnologies, the storage systems described above may also support thestorage and use of derivative items such as, for example, open sourceblockchains and related tools that are part of the IBM™ Hyperledgerproject, permissioned blockchains in which a certain number of trustedparties are allowed to access the block chain, blockchain products thatenable developers to build their own distributed ledger projects, andothers. Blockchains and the storage systems described herein may beleveraged to support on-chain storage of data as well as off-chainstorage of data.

Off-chain storage of data can be implemented in a variety of ways andcan occur when the data itself is not stored within the blockchain. Forexample, in one embodiment, a hash function may be utilized and the dataitself may be fed into the hash function to generate a hash value. Insuch an example, the hashes of large pieces of data may be embeddedwithin transactions, instead of the data itself. Readers will appreciatethat, in other embodiments, alternatives to blockchains may be used tofacilitate the decentralized storage of information. For example, onealternative to a blockchain that may be used is a blockweave. Whileconventional blockchains store every transaction to achieve validation,a blockweave permits secure decentralization without the usage of theentire chain, thereby enabling low cost on-chain storage of data. Suchblockweaves may utilize a consensus mechanism that is based on proof ofaccess (PoA) and proof of work (PoW).

The storage systems described above may, either alone or in combinationwith other computing devices, be used to support in-memory computingapplications. In-memory computing involves the storage of information inRAM that is distributed across a cluster of computers. Readers willappreciate that the storage systems described above, especially thosethat are configurable with customizable amounts of processing resources,storage resources, and memory resources (e.g., those systems in whichblades that contain configurable amounts of each type of resource), maybe configured in a way so as to provide an infrastructure that cansupport in-memory computing. Likewise, the storage systems describedabove may include component parts (e.g., NVDIMMs, 3D crosspoint storagethat provide fast random access memory that is persistent) that canactually provide for an improved in-memory computing environment ascompared to in-memory computing environments that rely on RAMdistributed across dedicated servers.

In some embodiments, the storage systems described above may beconfigured to operate as a hybrid in-memory computing environment thatincludes a universal interface to all storage media (e.g., RAM, flashstorage, 3D crosspoint storage). In such embodiments, users may have noknowledge regarding the details of where their data is stored but theycan still use the same full, unified API to address data. In suchembodiments, the storage system may (in the background) move data to thefastest layer available—including intelligently placing the data independence upon various characteristics of the data or in dependenceupon some other heuristic. In such an example, the storage systems mayeven make use of existing products such as Apache Ignite and GridGain tomove data between the various storage layers, or the storage systems maymake use of custom software to move data between the various storagelayers. The storage systems described herein may implement variousoptimizations to improve the performance of in-memory computing such as,for example, having computations occur as close to the data as possible.

Readers will further appreciate that in some embodiments, the storagesystems described above may be paired with other resources to supportthe applications described above. For example, one infrastructure couldinclude primary compute in the form of servers and workstations whichspecialize in using General-purpose computing on graphics processingunits (‘GPGPU’) to accelerate deep learning applications that areinterconnected into a computation engine to train parameters for deepneural networks. Each system may have Ethernet external connectivity,InfiniBand external connectivity, some other form of externalconnectivity, or some combination thereof. In such an example, the GPUscan be grouped for a single large training or used independently totrain multiple models. The infrastructure could also include a storagesystem such as those described above to provide, for example, ascale-out all-flash file or object store through which data can beaccessed via high-performance protocols such as NFS, S3, and so on. Theinfrastructure can also include, for example, redundant top-of-rackEthernet switches connected to storage and compute via ports in MLAGport channels for redundancy. The infrastructure could also includeadditional compute in the form of whitebox servers, optionally withGPUs, for data ingestion, pre-processing, and model debugging. Readerswill appreciate that additional infrastructures are also be possible.

Readers will appreciate that the storage systems described above, eitheralone or in coordination with other computing machinery may beconfigured to support other AI related tools. For example, the storagesystems may make use of tools like ONXX or other open neural networkexchange formats that make it easier to transfer models written indifferent AI frameworks. Likewise, the storage systems may be configuredto support tools like Amazon's Gluon that allow developers to prototype,build, and train deep learning models. In fact, the storage systemsdescribed above may be part of a larger platform, such as IBM™ CloudPrivate for Data, that includes integrated data science, dataengineering and application building services.

Readers will further appreciate that the storage systems described abovemay also be deployed as an edge solution. Such an edge solution may bein place to optimize cloud computing systems by performing dataprocessing at the edge of the network, near the source of the data. Edgecomputing can push applications, data and computing power (i.e.,services) away from centralized points to the logical extremes of anetwork. Through the use of edge solutions such as the storage systemsdescribed above, computational tasks may be performed using the computeresources provided by such storage systems, data may be storage usingthe storage resources of the storage system, and cloud-based servicesmay be accessed through the use of various resources of the storagesystem (including networking resources). By performing computationaltasks on the edge solution, storing data on the edge solution, andgenerally making use of the edge solution, the consumption of expensivecloud-based resources may be avoided and, in fact, performanceimprovements may be experienced relative to a heavier reliance oncloud-based resources.

While many tasks may benefit from the utilization of an edge solution,some particular uses may be especially suited for deployment in such anenvironment. For example, devices like drones, autonomous cars, robots,and others may require extremely rapid processing—so fast, in fact, thatsending data up to a cloud environment and back to receive dataprocessing support may simply be too slow. As an additional example,some IoT devices such as connected video cameras may not be well-suitedfor the utilization of cloud-based resources as it may be impractical(not only from a privacy perspective, security perspective, or afinancial perspective) to send the data to the cloud simply because ofthe pure volume of data that is involved. As such, many tasks thatreally on data processing, storage, or communications may be bettersuited by platforms that include edge solutions such as the storagesystems described above.

The storage systems described above may alone, or in combination withother computing resources, serves as a network edge platform thatcombines compute resources, storage resources, networking resources,cloud technologies and network virtualization technologies, and so on.As part of the network, the edge may take on characteristics similar toother network facilities, from the customer premise and backhaulaggregation facilities to Points of Presence (PoPs) and regional datacenters. Readers will appreciate that network workloads, such as VirtualNetwork Functions (VNFs) and others, will reside on the network edgeplatform. Enabled by a combination of containers and virtual machines,the network edge platform may rely on controllers and schedulers thatare no longer geographically co-located with the data processingresources. The functions, as microservices, may split into controlplanes, user and data planes, or even state machines, allowing forindependent optimization and scaling techniques to be applied. Such userand data planes may be enabled through increased accelerators, boththose residing in server platforms, such as FPGAs and Smart NICs, andthrough SDN-enabled merchant silicon and programmable ASICs.

The storage systems described above may also be optimized for use in bigdata analytics. Big data analytics may be generally described as theprocess of examining large and varied data sets to uncover hiddenpatterns, unknown correlations, market trends, customer preferences andother useful information that can help organizations make more-informedbusiness decisions. As part of that process, semi-structured andunstructured data such as, for example, internet clickstream data, webserver logs, social media content, text from customer emails and surveyresponses, mobile-phone call-detail records, IoT sensor data, and otherdata may be converted to a structured form.

The storage systems described above may also support (includingimplementing as a system interface) applications that perform tasks inresponse to human speech. For example, the storage systems may supportthe execution intelligent personal assistant applications such as, forexample, Amazon's Alexa, Apple Siri, Google Voice, Samsung Bixby,Microsoft Cortana, and others. While the examples described in theprevious sentence make use of voice as input, the storage systemsdescribed above may also support chatbots, talkbots, chatterbots, orartificial conversational entities or other applications that areconfigured to conduct a conversation via auditory or textual methods.Likewise, the storage system may actually execute such an application toenable a user such as a system administrator to interact with thestorage system via speech. Such applications are generally capable ofvoice interaction, music playback, making to-do lists, setting alarms,streaming podcasts, playing audiobooks, and providing weather, traffic,and other real time information, such as news, although in embodimentsin accordance with the present disclosure, such applications may beutilized as interfaces to various system management operations.

The storage systems described above may also implement AI platforms fordelivering on the vision of self-driving storage. Such AI platforms maybe configured to deliver global predictive intelligence by collectingand analyzing large amounts of storage system telemetry data points toenable effortless management, analytics and support. In fact, suchstorage systems may be capable of predicting both capacity andperformance, as well as generating intelligent advice on workloaddeployment, interaction and optimization. Such AI platforms may beconfigured to scan all incoming storage system telemetry data against alibrary of issue fingerprints to predict and resolve incidents inreal-time, before they impact customer environments, and captureshundreds of variables related to performance that are used to forecastperformance load.

The storage systems described above may support the serialized orsimultaneous execution of artificial intelligence applications, machinelearning applications, data analytics applications, datatransformations, and other tasks that collectively may form an AIladder. Such an AI ladder may effectively be formed by combining suchelements to form a complete data science pipeline, where existdependencies between elements of the AI ladder. For example, AI mayrequire that some form of machine learning has taken place, machinelearning may require that some form of analytics has taken place,analytics may require that some form of data and informationarchitecting has taken place, and so on. As such, each element may beviewed as a rung in an AI ladder that collectively can form a completeand sophisticated AI solution.

The storage systems described above may also, either alone or incombination with other computing environments, be used to deliver an AIeverywhere experience where AI permeates wide and expansive aspects ofbusiness and life. For example, AI may play an important role in thedelivery of deep learning solutions, deep reinforcement learningsolutions, artificial general intelligence solutions, autonomousvehicles, cognitive computing solutions, commercial UAVs or drones,conversational user interfaces, enterprise taxonomies, ontologymanagement solutions, machine learning solutions, smart dust, smartrobots, smart workplaces, and many others.

The storage systems described above may also, either alone or incombination with other computing environments, be used to deliver a widerange of transparently immersive experiences (including those that usedigital twins of various “things” such as people, places, processes,systems, and so on) where technology can introduce transparency betweenpeople, businesses, and things. Such transparently immersive experiencesmay be delivered as augmented reality technologies, connected homes,virtual reality technologies, brain-computer interfaces, humanaugmentation technologies, nanotube electronics, volumetric displays, 4Dprinting technologies, or others.

The storage systems described above may also, either alone or incombination with other computing environments, be used to support a widevariety of digital platforms. Such digital platforms can include, forexample, 5G wireless systems and platforms, digital twin platforms, edgecomputing platforms, IoT platforms, quantum computing platforms,serverless PaaS, software-defined security, neuromorphic computingplatforms, and so on.

The storage systems described above may also be part of a multi-cloudenvironment in which multiple cloud computing and storage services aredeployed in a single heterogeneous architecture. In order to facilitatethe operation of such a multi-cloud environment, DevOps tools may bedeployed to enable orchestration across clouds. Likewise, continuousdevelopment and continuous integration tools may be deployed tostandardize processes around continuous integration and delivery, newfeature rollout and provisioning cloud workloads. By standardizing theseprocesses, a multi-cloud strategy may be implemented that enables theutilization of the best provider for each workload.

The storage systems described above may be used as a part of a platformto enable the use of crypto-anchors that may be used to authenticate aproduct's origins and contents to ensure that it matches a blockchainrecord associated with the product. Similarly, as part of a suite oftools to secure data stored on the storage system, the storage systemsdescribed above may implement various encryption technologies andschemes, including lattice cryptography. Lattice cryptography caninvolve constructions of cryptographic primitives that involve lattices,either in the construction itself or in the security proof. Unlikepublic-key schemes such as the RSA, Diffie-Hellman or Elliptic-Curvecryptosystems, which are easily attacked by a quantum computer, somelattice-based constructions appear to be resistant to attack by bothclassical and quantum computers.

A quantum computer is a device that performs quantum computing. Quantumcomputing is computing using quantum-mechanical phenomena, such assuperposition and entanglement. Quantum computers differ fromtraditional computers that are based on transistors, as such traditionalcomputers require that data be encoded into binary digits (bits), eachof which is always in one of two definite states (0 or 1). In contrastto traditional computers, quantum computers use quantum bits, which canbe in superpositions of states. A quantum computer maintains a sequenceof qubits, where a single qubit can represent a one, a zero, or anyquantum superposition of those two qubit states. A pair of qubits can bein any quantum superposition of 4 states, and three qubits in anysuperposition of 8 states. A quantum computer with n qubits cangenerally be in an arbitrary superposition of up to 2{circumflex over( )}n different states simultaneously, whereas a traditional computercan only be in one of these states at any one time. A quantum Turingmachine is a theoretical model of such a computer.

The storage systems described above may also be paired withFPGA-accelerated servers as part of a larger AI or ML infrastructure.Such FPGA-accelerated servers may reside near (e.g., in the same datacenter) the storage systems described above or even incorporated into anappliance that includes one or more storage systems, one or moreFPGA-accelerated servers, networking infrastructure that supportscommunications between the one or more storage systems and the one ormore FPGA-accelerated servers, as well as other hardware and softwarecomponents. Alternatively, FPGA-accelerated servers may reside within acloud computing environment that may be used to perform compute-relatedtasks for AI and ML jobs. Any of the embodiments described above may beused to collectively serve as a FPGA-based AI or ML platform. Readerswill appreciate that, in some embodiments of the FPGA-based AI or MLplatform, the FPGAs that are contained within the FPGA-acceleratedservers may be reconfigured for different types of ML models (e.g.,LSTMs, CNNs, GRUs). The ability to reconfigure the FPGAs that arecontained within the FPGA-accelerated servers may enable theacceleration of a ML or AI application based on the most optimalnumerical precision and memory model being used. Readers will appreciatethat by treating the collection of FPGA-accelerated servers as a pool ofFPGAs, any CPU in the data center may utilize the pool of FPGAs as ashared hardware microservice, rather than limiting a server to dedicatedaccelerators plugged into it.

The FPGA-accelerated servers and the GPU-accelerated servers describedabove may implement a model of computing where, rather than keeping asmall amount of data in a CPU and running a long stream of instructionsover it as occurred in more traditional computing models, the machinelearning model and parameters are pinned into the high-bandwidth on-chipmemory with lots of data streaming though the high-bandwidth on-chipmemory. FPGAs may even be more efficient than GPUs for this computingmodel, as the FPGAs can be programmed with only the instructions neededto run this kind of computing model.

The storage systems described above may be configured to provideparallel storage, for example, through the use of a parallel file systemsuch as BeeGFS. Such parallel files systems may include a distributedmetadata architecture. For example, the parallel file system may includea plurality of metadata servers across which metadata is distributed, aswell as components that include services for clients and storageservers.

The systems described above can support the execution of a wide array ofsoftware applications. Such software applications can be deployed in avariety of ways, including container-based deployment models.Containerized applications may be managed using a variety of tools. Forexample, containerized applications may be managed using Docker Swarm,Kubernetes, and others. Containerized applications may be used tofacilitate a serverless, cloud native computing deployment andmanagement model for software applications. In support of a serverless,cloud native computing deployment and management model for softwareapplications, containers may be used as part of an event handlingmechanisms (e.g., AWS Lambdas) such that various events cause acontainerized application to be spun up to operate as an event handler.

The systems described above may be deployed in a variety of ways,including being deployed in ways that support fifth generation (‘5G’)networks. 5G networks may support substantially faster datacommunications than previous generations of mobile communicationsnetworks and, as a consequence may lead to the disaggregation of dataand computing resources as modern massive data centers may become lessprominent and may be replaced, for example, by more-local, micro datacenters that are close to the mobile-network towers. The systemsdescribed above may be included in such local, micro data centers andmay be part of or paired to multi-access edge computing (‘MEC’) systems.Such MEC systems may enable cloud computing capabilities and an ITservice environment at the edge of the cellular network. By runningapplications and performing related processing tasks closer to thecellular customer, network congestion may be reduced and applicationsmay perform better.

For further explanation, FIG. 3D illustrates an exemplary computingdevice 350 that may be specifically configured to perform one or more ofthe processes described herein. As shown in FIG. 3D, computing device350 may include a communication interface 352, a processor 354, astorage device 356, and an input/output (“I/O”) module 358communicatively connected one to another via a communicationinfrastructure 360. While an exemplary computing device 350 is shown inFIG. 3D, the components illustrated in FIG. 3D are not intended to belimiting. Additional or alternative components may be used in otherembodiments. Components of computing device 350 shown in FIG. 3D willnow be described in additional detail.

Communication interface 352 may be configured to communicate with one ormore computing devices. Examples of communication interface 352 include,without limitation, a wired network interface (such as a networkinterface card), a wireless network interface (such as a wirelessnetwork interface card), a modem, an audio/video connection, and anyother suitable interface.

Processor 354 generally represents any type or form of processing unitcapable of processing data and/or interpreting, executing, and/ordirecting execution of one or more of the instructions, processes,and/or operations described herein. Processor 354 may perform operationsby executing computer-executable instructions 362 (e.g., an application,software, code, and/or other executable data instance) stored in storagedevice 356.

Storage device 356 may include one or more data storage media, devices,or configurations and may employ any type, form, and combination of datastorage media and/or device. For example, storage device 356 mayinclude, but is not limited to, any combination of the non-volatilemedia and/or volatile media described herein. Electronic data, includingdata described herein, may be temporarily and/or permanently stored instorage device 356. For example, data representative ofcomputer-executable instructions 362 configured to direct processor 354to perform any of the operations described herein may be stored withinstorage device 356. In some examples, data may be arranged in one ormore databases residing within storage device 356.

I/O module 358 may include one or more I/O modules configured to receiveuser input and provide user output. I/O module 358 may include anyhardware, firmware, software, or combination thereof supportive of inputand output capabilities. For example, I/O module 358 may includehardware and/or software for capturing user input, including, but notlimited to, a keyboard or keypad, a touchscreen component (e.g.,touchscreen display), a receiver (e.g., an RF or infrared receiver),motion sensors, and/or one or more input buttons.

I/O module 358 may include one or more devices for presenting output toa user, including, but not limited to, a graphics engine, a display(e.g., a display screen), one or more output drivers (e.g., displaydrivers), one or more audio speakers, and one or more audio drivers. Incertain embodiments, I/O module 358 is configured to provide graphicaldata to a display for presentation to a user. The graphical data may berepresentative of one or more graphical user interfaces and/or any othergraphical content as may serve a particular implementation. In someexamples, any of the systems, computing devices, and/or other componentsdescribed herein may be implemented by computing device 350.

In some examples, a non-transitory computer-readable medium storingcomputer-readable instructions may be provided in accordance with theprinciples described herein. The instructions, when executed by aprocessor of a computing device, may direct the processor and/orcomputing device to perform one or more operations, including one ormore of the operations described herein. Such instructions may be storedand/or transmitted using any of a variety of known computer-readablemedia.

A non-transitory computer-readable medium as referred to herein mayinclude any non-transitory storage medium that participates in providingdata (e.g., instructions) that may be read and/or executed by acomputing device (e.g., by a processor of a computing device). Forexample, a non-transitory computer-readable medium may include, but isnot limited to, any combination of non-volatile storage media and/orvolatile storage media. Exemplary non-volatile storage media include,but are not limited to, read-only memory, flash memory, a solid-statedrive, a magnetic storage device (e.g. a hard disk, a floppy disk,magnetic tape, etc.), ferroelectric random-access memory (“RAM”), and anoptical disc (e.g., a compact disc, a digital video disc, a Blu-raydisc, etc.). Exemplary volatile storage media include, but are notlimited to, RAM (e.g., dynamic RAM).

Advantages and features of the present disclosure can be furtherdescribed by the following statements:

1. A data storage system comprising: a memory storing instructions; anda processor communicatively coupled to the memory and configured toexecute the instructions to: establish a path set that represents acollection of storage layer entities associated with service layerentities of a directory hierarchy of a file system; and coordinate,based on the path set and on operations applied to one or more of theservice layer entities of the directory hierarchy of the file system,implementation of the operations on the storage layer entities.

2. The data storage system of statement 1, wherein the service layerentities comprise files and directories within the directory hierarchyof the file system; and the storage layer entities comprise blockobjects implementing the files and directories.

3. The data storage system of any of the preceding statements, whereinthe operations comprise a snapshot of a directory associated with thedirectory hierarchy of the file system; and the coordinatingimplementation of the operations on the storage layer entities comprisesimplementing the snapshot on a storage implementation entity of thestorage layer entities in response to a request to modify the storagelayer entity.

4. The data storage system of any of the preceding statements, whereinthe snapshot is applied to the directory at a first time; and theimplementation of the snapshot on the storage layer entity is delayeduntil a modification of the storage layer entity is requested at asecond time subsequent to the first time.

5. The data storage system of any of the preceding statements, whereinthe request to modify the storage layer entity comprises a request todelete the storage layer entity or a request to write to the data or themetadata of the storage layer entity.

6. The data storage system of any of the preceding statements, whereinthe operations further comprise a snapshot of a subdirectory of thedirectory associated with the directory hierarchy of the file system;and the coordinating implementation of the operations on the storagelayer entities comprises implementing the snapshot of the subdirectoryon the storage layer entity in response to the request to modify thestorage layer entity.

7. The data storage system of any of the preceding statements, whereinthe processor is configured to execute the instructions to establish anadditional path set that represents an additional collection of storagelayer entities associated with service layer entities of the directoryhierarchy of the file system; the path set corresponds to a firstoperation of the operations, the first operation applied, at a firsttime, to the directory hierarchy of the file system; and the additionalpath set corresponds to a second operation of the operations, the secondoperation applied, at a second time subsequent to the first time, to thedirectory hierarchy of the file system.

8. The data storage system of any of the preceding statements, whereinthe path set represents the collection of storage layer entities thatare associated with service layer entities of the directory hierarchy ofthe file system at the first time; and the additional path setrepresents the additional collection of storage layer entities that areassociated with service layer entities of the directory hierarchy of thefile system at the second time.

9. The data storage system of any of the preceding statements, whereinthe additional collection of storage layer entities that are associatedwith service layer entities of the directory hierarchy of the filesystem at the second time is different from the collection of storagelayer entities that are associated with service layer entities of thedirectory hierarchy of the file system at the first time.

10. The data storage system of any of the preceding statements, whereinthe directory hierarchy of the file system is associated with a manageddirectory designated to be managed with path sets.

11. The data storage system of any of the preceding statements, whereinthe service layer entities are managed by a service layer of the datastorage system, the service layer configured to provide a data storageservice; the storage layer entities are managed by a storage layer ofthe data storage system; and certain aspects of the data storage serviceare separated from the service layer for implementation by the storagelayer.

12. The data storage system of any of the preceding statements, whereinthe service layer maintains configuration information representing thedirectory hierarchy of the file system; and the storage layer entitiesof the storage layer do not maintain configuration informationrepresenting the directory hierarchy of the file system.

13. The data storage system of any of the preceding statements, whereinthe operations comprise at least one of a snapshot operation, a cloningoperation, a replication operation, a continuous data protectionoperation, a quota operation, a space management operation, or a spaceaccounting operation.

14. A data storage system comprising: a memory storing instructions; anda processor communicatively coupled to the memory and configured toexecute the instructions to: establish that an operation applied to adirectory hierarchy of a file system at a first time is to beselectively implemented later in time; detect a request to modify astorage layer entity at a second time that is after the first time; andimplement, in response to the request and based on a path set indicatingthat the storage layer entity is associated with the directory hierarchyof the file system at the first time, the operation on the storage layerentity before modifying the storage layer entity based on the request.

15. The data storage system of any of the preceding statements, whereinthe operation comprises a snapshot of the directory hierarchy.

16. The data storage system of any of the preceding statements, whereinthe storage layer entity comprises a block object that implements a fileor directory of the directory hierarchy of the file system.

17. The data storage system of any of the preceding statements, whereinthe path set indicates any managed directory of the file system having adirectory tree that includes the file or directory implemented by theblock object.

18. A method comprising: receiving a request to modify a storage layerentity that implements a file service layer entity of a file system;determining, in response to the request and based on a path setindicating a relationship between the storage layer entity and adirectory of the file system, that there is a pending operation on thedirectory that is yet to be applied to the storage layer entity; andapplying, based on the determining, the pending action to the storagelayer entity before modifying the storage layer entity based on therequest.

19. The method of any of the preceding statements, wherein the pendingaction comprises a snapshot of the directory.

20. The method of any of the preceding statements, wherein the storagelayer entity comprises a block object that implements a file ordirectory of a directory hierarchy of the directory of the file system.

One or more embodiments may be described herein with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

While particular combinations of various functions and features of theone or more embodiments are expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

In accordance with certain embodiments of the present disclosure, astorage system may provide unified data storage on block containers and,using the unified storage on block containers, may provide one or moredata storage services such as block, file, object, and/or databaseservices. To this end, the storage system may leverage block containersand one or more resources associated with block containers such that adata storage service provided by the storage system benefits from and/orhas access to block containers and resources associated with blockcontainers. In certain examples, this may allow block containers thatare optimized for implementation using all-flash data storage to be usedto provide one or more data storage services that are similarlyoptimized for implementation using all-flash data storage. The storagesystem may provide and/or facilitate efficient operations on blockcontainers and container data, such as efficient writing, reading,extending, thin-provisioning, deleting, range-copying, mapping,unmapping, snapshotting, cloning, replicating, compressing,deduplicating, garbage collecting, etc.

FIGS. 4A-4B illustrate an example of a data storage system 400 thatincludes a block container system 402 and a container utilization system404 communicatively coupled to one another. Block container system 402and container utilization system 404 may be communicatively coupledusing any suitable data communication technologies.

Block container system 402 may provide block containers 405 andresources 406 associated with block containers 405. Block containers 405may represent a linear address space of blocks where block containersystem 402 may quickly and dynamically create and delete blockcontainers. Block containers 405 may be thin provisioned with a blockrange deallocate capability. The block address space may be any suitablesize, including very large (e.g., a 64-bit address space of bytes orblocks) in some examples. Implementations of block containers 405 maysupport operations and/or sharing or stored content within and betweenblock containers 405, such as operations or sharing of stored contentacross block containers of different types (e.g., across blockcontainers of different forms used for different types of storagesystems). Examples of such operations or sharing of stored contentinclude, without limitation, snapshots, clones, checkpoints,replication, deduplication, compression, encryption, and virtual copy byreference operations for entire block containers (e.g., cloning byreference the content of one block container to another) as well as forranges of blocks within and between block containers. Block containers405 may be tagged, grouped, and/or named to allow operations ormechanisms such as snapshots, clones, checkpoints, and replication tooperate consistently and atomically on various types of sets of blockcontainers 405 to form or replace matching sets of block containers 405.Such features may facilitate grouping of individual block containers 405or sets of block containers 405 into groups.

An example of such a group may be referred to as a “pod.” A pod mayrepresent a dataset along with one or more storage systems that storethe dataset. A pod may have a name and an identifier. Storage systemsmay be added to and removed from a pod. When a storage system is addedto a pod, the pod's dataset may be copied to that storage system andthen kept up to data as the dataset is modified. When a storage systemis removed from a pod, the pod's dataset is no longer kept up to date onthe storage system. Any storage system that is active for a pod canreceive and process requests to modify or read the pod. A pod may alsobe a unit of administration that represents a collection of blockcontainers 405, volumes, file systems, object/analytic stores,snapshots, and other administrative entities where making administrativechanges on any one storage system is automatically reflected to allactive storage systems associated with the pod. In the context ofstorage systems described herein, a pod may operate as a namespace forsome set of objects (for example, block containers or snapshots orclones of block containers) that can be operated on as a set, such thatadditions or removals of a set of objects (such as block containers)from the pod causes future operations to operate on the adjustedcollection of these objects. If a pod is replicated, such as throughsymmetric synchronous replication, between storage systems, then eachstorage system which is operating normally against the pod will storethe same collection of these objects with the same names and otheridentify or tag metadata.

In certain examples, implementations of block containers 405 mayoptimize data storage system 400 for flash data storage (e.g., all-flashdata storage). For example, block container system 402 may be configuredto generally gather a collection of updates which will be organized intosegments (e.g., medium-sized segments) that are written and managed insuch a way that the content and the capacity held by the stored segmentsare changed or reused through a garbage collection process. Segments maybe any suitable size, such as on the order of megabytes, and may besized optimally around flash erase blocks or sized optimally for erasurecoded segments written as shards across several flash-based storagedevices which are organized as erase blocks or to be a reasonablyoptimal size for desired throughput in writing and reading whole datastructures in a data store operating as a bulk backend for data storagesystem 400 and/or a data storage service provided by data storage system400 (e.g., writing and reading whole objects in an object storeoperating as a build backend for data storage system 400). Such segmentscan work with flash-based data storage that exposes erase blocksdirectly or through some scheme such as zoned drives. Such a scheme canalso be used to organize data to be written (and eventually garbagecollected) to non-flash-based zoned drives or to medium-sized objects ina typical type of object store that best supports objects which arewritten and eventually deleted without ever having been updated inplace.

In certain embodiments, block container system 402 may include and/ormay be specifically designed to use all-flash data storage forblock-based data storage. To this end, block container system 402 may bea flash block-based storage system that is optimized for flashblock-based storage and that preserves data integrity, providesconsistent low latency and high performance, and maximizes physicalmedia endurance.

Resources 406 associated with block containers 405 may include anycomponents of block container system 402 configured to create, delete,modify, thin provision, allocate, deallocate, append, or otherwiseoperate on block containers 405 and/or content of block containers 405.Resources 406 may be implemented in any suitable way, including ashardware and/or software components (e.g., as computer-implementedinstructions executable by a processor to perform operations on blockcontainers 405). Resources 406 may include any of the storage systemresources described herein, including any of storage resources 308,communications resources 310, processing resources 312, softwareresources 314, and other resources described above. Examples ofresources 406 of block container system 402 include, without limitation,data reduction resources (e.g., pattern removal, deduplication, andcompression resources), metadata resources (e.g., metadata such as oneor more maps that track relationships between logical block addressesand physical media addresses), data structure resources (e.g., graphs ofstructures called logical extents), data replication resources (e.g.,snapshot, clone, extended copy, asynchronous replication, synchronousreplication resources), storage reclamation resources (e.g., garbagecollection resources), lookaside data structure resources for trackingoperations on data for use in implementing or completing implementationof changes in a time-shifted manner (e.g., by a background process at asuitable time), foreground or inline data processing resources (e.g.,foreground or inline data reduction as part of a data write process),and background processing resources (e.g., background data reduction,storage reclamation, etc. applied to logically stored data that remainsunaltered for a threshold length of time). Examples of resources 406 ofblock container system 402 may include components and/or processesconfigured to perform operations such as writing, reading, extending,thin-provisioning, deleting, range-copying, mapping, unmapping,snapshotting, cloning, replicating, compressing, deduplicating, andgarbage collecting block containers 405 and/or content of blockcontainers 405.

Block containers 405 may be configured to store and address data inblocks of any suitable size and configuration. Accordingly, blockcontainers system 402 may utilize block containers 405 for multipletypes of uses. In certain implementations, block containers 405 may beused to represent volumes, which may function to a client host asindividual data storage drives accessed through SCSI, NVMe, or someother block protocol (e.g., mounted drive volumes accessible by anoperating system). In certain implementations, block containers 405 mayadditionally or alternatively include or represent fixed or variablesize blocks of data that each contain a number of sectors of data (e.g.,zero or more 512-byte sectors of data).

Block container system 402 may include or implement any of the storagesystems or features of the storage systems described above. In certainembodiments, block container system 402 may include a virtually mappedallocate-on-write and/or copy-on-write block-based storage system.

Block containers 405 may be implemented in any way suitable to provideone or more of the features of block container system 402 describedherein. Examples of architectures for implementing block containers 405will now be described. The examples are illustrative and not limiting.Additional or alternative architectures for implementing blockcontainers 405 may be used in other examples.

In certain examples, block containers 405 may be implemented using alinear table of vectors to blocks or content-addressable stores. Incertain examples, block containers 405 may be implemented using atwo-level vector of block references where blocks themselves arecompressed and written into garbage collection segments. In certainimplementations, the two-level vector may use copy-on-write of a moregranular vector level. In certain examples, block containers 405 may beimplemented using hash references (e.g., hash tables) to blocks orcontent-addressable stores. In certain examples, block containers 405may be implemented using B-trees or similar data structures thatreference blocks or content-addressable stores.

In certain examples, block containers 405 may be implemented usinggraphs of structures called logical extents. A logical extent mayinclude a list of pointers to logical block addresses, to other logicalextents, or to a combination of logical block addresses and otherlogical extents. Logical extents may be linked together to form a datastructure such as graph of logical extent nodes that representsrelationships between data. Any suitable structure of logical extentsmay be used, such as an acyclic graph of logical extents. In certainexamples, block container system 402 may use a directed acyclic graph(DAG′) or a balanced directed acyclic graph (‘B-DAG’) of logicalextents.

In certain examples, logical extents may be categorized into two typesof logical extents: leaf logical extents that reference some amount ofstored data in some way (e.g., by including or pointing to logicaladdresses mapped to physical media locations of data) and compositelogical extents that reference other leaf or composite logical extents.

A leaf extent can reference data in a variety of ways. It can pointdirectly to a single range of stored data (e.g., 64 kilobytes of data),or it can be a collection of references to stored data (e.g., a 1megabyte “range” of content that maps some number of virtual blocksassociated with the range to physically stored blocks). In the lattercase, these blocks may be referenced using some identity, and someblocks within the range of the extent may not be mapped to anything.Also in the latter case, these block references need not be unique,allowing multiple mappings from virtual blocks within some number oflogical extents within and across some number of block containers (e.g.,block containers 405) to map to the same physically stored blocks.Instead of stored block references, a logical extent could encode simplepatterns. For example, a block that is a string of identical bytes couldsimply encode that the block is a repeated pattern of identical bytes.

A composite logical extent can be a logical range of content with somevirtual size, which comprises a plurality of maps that each map from asubrange of the composite logical extent logical range of content to anunderlying leaf or composite logical extent. Transforming a requestrelated to content for a composite logical extent, then, involves takingthe content range for the request within the context of the compositelogical extent, determining which underlying leaf or composite logicalextents that request maps to, and transforming the request to apply toan appropriate range of content within those underlying leaf orcomposite logical extents.

In certain implementations of block container system 402, blockcontainers can be defined as logical extents. Thus, block containers canbe organized using the logical extent model. In certain examples, agraph of logical extents may include a root node associated with a blockcontainer in block container system 402. The root node may point to oneor more other nodes that point to other nodes and/or logical addressesmapped to physical media locations at which data associated with theblock container is stored.

Depending on implementation, leaf or composite logical extents could bereferenced from a plurality of other composite logical extents,effectively allowing inexpensive duplication of larger collections ofcontent within and across block containers. Thus, logical extents can bearranged essentially within an acyclic graph of references, each endingin leaf logical extents. This can be used to make copies of blockcontainers, to make snapshots of block containers, or as part ofsupporting virtual range copies within and between block containers aspart of an extended copy operation or similar types of operations.

An implementation may provide each logical extent with an identity whichcan be used to name it. This simplifies referencing, since thereferences within composite logical extents become lists comprisinglogical extent identities and a logical subrange corresponding to eachsuch logical extent identity. Within logical extents, each stored datablock reference may also be based on some identity used to name it.

To support these duplicated uses of extents, logical extents may beconfigured as copy-on-write logical extents. When a data modifyingoperation affects a copy-on-write leaf or composite logical extent, thelogical extent is copied, with the copy being a new reference andpossibly having a new identity (depending on implementation). The copyretains all references or identities related to underlying leaf orcomposite logical extents, but with whatever modifications result fromthe modifying operation. For example, a write request, a write samerequest, an extended write read request, an extended write request, or acompare and write request may store new blocks in the storage system (oruse deduplication techniques to identify existing stored blocks),resulting in modifying the corresponding leaf logical extents toreference or store identities to a new set of blocks, possibly replacingreferences and stored identities for a previous set of blocks.Alternately, an un-map request may modify a leaf logical extent toremove one or more block references. In both types of cases, a leaflogical extent is modified. If the leaf logical extent is acopy-on-write logical extent, then a new leaf logical extent will becreated that is formed by copying unaffected block references from theold extent and then replacing or removing block references based on themodifying operation.

A composite logical extent that was used to locate the leaf logicalextent may then be modified to store the new leaf logical extentreference or identity associated with the copied and modified leaflogical extent as a replacement for the previous leaf logical extent. Ifthat composite logical extent is a copy-on-write logical extent, then anew composite logical extent is created as a new reference or with a newidentity, and any unaffected references or identities to its underlyinglogical extents are copied to that new composite logical extent, withthe previous leaf logical extent reference or identity being replacedwith the new leaf logical extent reference or identity.

This process continues further backward from referenced extent toreferencing composite extent, based on the search path through theacyclic graph used to process the modifying operation, with allcopy-on-write logical extents being copied, modified, and replaced.

These copied leaf and composite logical extents can then drop thecharacteristic of being copy on write, so that further modifications donot result in a copy. For example, the first time some underlyinglogical extent within a copy-on-write “parent” composite extent ismodified, that underlying logical extent may be copied and modified,with the copy having a new identity which is then written into a copiedand replaced instance of the parent composite logical extent. But, asecond time some other underlying logical extent is copied and modifiedand with that other underlying logical extent copy's new identity beingwritten to the parent composite logical extent, the parent can then bemodified in place with no further copy and replace necessary on behalfof references to the parent composite logical extent.

Modifying operations to new regions of a block container or of acomposite logical extent for which there is no current leaf logicalextent may create a new leaf logical extent to store the results ofthose modifications. If that new logical extent is to be referenced froman existing copy-on-write composite logical extent, then that existingcopy-on-write composite logical extent will be modified to reference thenew logical extent, resulting in another copy, modify, and replacesequence of operations similar to the sequence for modifying an existingleaf logical extent.

If a parent composite logical extent cannot be grown large enough (basedon implementation) to cover an address range associated with new leaflogical extents to be created for a new modifying operation, then theparent composite logical extent may be copied into two or more newcomposite logical extents which are then referenced from a single“grandparent” composite logical extent which yet again is a newreference or a new identity. If that grandparent logical extent isitself found through another composite logical extent that is acopy-on-write logical extent, then that other composite logical extentwill be copied and modified and replaced in a similar way as describedin previous paragraphs.

This copy-on-write model can be used as part of implementing snapshots,block container copies, and virtual block container address range copieswithin a storage system implementation based on these directed acyclicgraphs of logical extents. To make a snapshot as a read-only copy of anotherwise writable block container, a graph of logical extentsassociated with the block container is marked copy-on-write andreferences to the original composite logical extents are retained by thesnapshot. Modifying operations to the block container will then makelogical extent copies as needed, resulting in the block containerstoring the results of those modifying operations and the snapshotsretaining the original content. Block container copies are similar,except that both the original block container and the copied blockcontainer can modify content resulting in their own copied logicalextent graphs and subgraphs.

Virtual block container address range copies can operate either bycopying block references within and between leaf logical extents (whichdoes not itself involve using copy-on-write techniques unless changes toblock references modify copy-on-write leaf logical extents).Alternately, virtual block container address range copies can duplicatereferences to leaf or composite logical extents. This works well forblock container address range copies of larger address ranges. And, thisis one way the graphs can become directed acyclic graphs of referencesrather than merely reference trees. Copy-on-write techniques associatedwith duplicated logical extent references can be used to ensure thatmodifying operations to the source or target of a virtual address rangecopy will result in the creation of new logical extents to store thosemodifications without affecting the target or the source that share thesame logical extent immediately after the block container address rangecopy operation.

Logical extents, such as described above, are an example of anarchitecture for implementing block containers 405. Another exampleincludes single-instance stores, where blocks are stored in associationwith an index derived from a secure hash fingerprint of their contentand where a block container would effectively be an array of referencesthat is updated whenever a block is written. A simple two-level logicalextent model, where one level represents a vector of references toindividual leaf logical extents represents a simpler version of thelogical extent model where the leaf logical extents can reference adeduplicated block store or a content addressable block store. Whateverthe model, the relationship between data stored into block containers405 at particular logical block addresses and bulk storage should bedynamic to ensure that new data is written into new blocks that arearranged within medium-sized segments, and organized around garbagecollection processes that can move blocks that are still referencedwhile deleting blocks that are no longer referenced in order to eitherreclaim space from segments that contain some no longer referencedblocks or, particularly in the case of flash memory, in order to addressflash memory durability issues.

Block container system 402 may be configured to present handles to blockcontainers 405. The handles may include any suitable data identifyingblock containers 405 such as pointers to block containers 405 (e.g.,pointers to root nodes of block containers 405). The handles may be usedby container utilization system 404 to operate on and/or interact withblock containers 405, such as by writing content to and/or readingcontent from block containers 405.

Container utilization system 404 may be configured to utilize blockcontainers 405 to store and manage content for one or more data storageservices provided by a unified data storage system. As an example, for ablock storage service, a block volume may be implemented on a singleblock container 405 (a block container representing a volume). Asanother example, for a file storage service, individual files,directories, file system data, and/or metadata may be implemented onindividual block containers 405. As another example, for an objectstorage service, individual objects and metadata may be implemented onindividual block containers 405. As another example, for a database,block containers 405 may be allocated to store individual redo logs,archive logs, table spaces, blobs (binary large objects), dataconfiguration data, and/or metadata.

To this end, container utilization system 404 may be configured to useblock containers 405 of block container system 402, as well as resources406 of block container system 402 in some examples, to provide one ormore data stores for storing and managing content for one or more datastorage services. For example, container utilization system 404 mayprovide a data store 408 that utilizes block containers 405 to representdata stored in data store 408. Accordingly, data store 408 may bereferred to as a container-based data store 408 for storing and managingcontent for a data storage service. Data store 408 may operate as a bulkbackend data store for one or more data storage services.

Container utilization system 404 may be configured to facilitate use ofblock containers 405 to represent data for any suitable number and/ortype of data storage services. To this end, container utilization system404 may provide and maintain any suitable number and types of datastores for storing content for any suitable number and/or type of datastorage services. In at least this regard, data storage system 400 maybe a unified storage system that supports various types of data storageservices and/or data storage protocols. For example, containerutilization system 404 may provide one or more data stores 408 forstoring content for block, file, object, and/or database storageservices.

Block containers 405 of block container system 402 may be adapted and/orused differently by container utilization system 404 for various datastorage services. For example, certain block containers 405 may be usedto represent content for a first storage service (e.g., a block storageservice), certain block containers 405 may be used to represent contentfor a second storage service different from the first storage service(e.g., a file storage service), etc.

In certain embodiments in which block containers 405 are implementedusing graphs of logical extents as described above, containerutilization system 404 may be configured to use graphs of logicalextents to represent and manage data in data store 408. For example, adata instance for a data storage service may be represented as a blockcontainer defined by a graph of logical extents that point to and/orinclude data for the data instance. Container utilization system 404 mayassociate the data instance with the block container defined by thegraph of logical extents, such as by associating an identifier for thedata instance with a root node of the graph of logical extents.

FIG. 5 illustrates an example of a block container 500 used to representa data instance in accordance with some embodiments. As shown in FIG. 5,block container 500 may include a graph (e.g., an acyclic graph such asa directed acyclic graph or a balanced directed acyclic graph) oflogical extent nodes 502-1 through 502-3 (collectively “logical extentnodes 502,” “logical extents 502,” or “nodes 502”). In the illustratedgraph, node 502-1 is a root node, node 502-2 is a child node of node502-1, and node 503-3 is a child node of node 502-2.

The graph of logical extents is associated with and represents a datainstance. In the illustrated example, a data instance identifier (dataID) 506 is mapped to root node 502-1 to associate a data instance havingthe data ID 506 to the root node 502-1 and consequently to the graph oflogical extents 502. Data ID 506 may be any suitable unique identifierand may be produced in any suitable way. For example, containerutilization system 404 may generate or receive data ID 506. Containerutilization system 404 may map the data ID 506 to root node 502-1 in anysuitable way.

Each of nodes 502 includes a list of one or more pointers to other nodes502 and/or to logical addresses mapped to physical media locations atwhich data associated with the data object is stored. For example, rootnode 502-1 may include a pointer to node 502-2, which may include apointer to node 502-3. Node 502-3 may include pointers to logicaladdresses such as logical block addresses that are mapped to locationsin physical media at which data for the object is stored. In FIG. 5,mediums 504-1 through 504-3 (collectively “mediums 504”) may representthe logical addresses (in a linear address space) and/or locations inphysical media at which data for the data instance is stored.Accordingly, nodes 502-1 and 502-2 may be composite logical extents, andnode 502-3 may be a leaf logical extent.

While FIG. 5 depicts a data ID 506 for a data instance being mapped toroot node 502-1, this is illustrative of certain embodiments. A datainstance may be associated with a graph of logical extents in anysuitable way, including by directly mapping the data instance to anyother suitable internal handle for supporting virtualized thinprovisioning of block containers 405 and/or blocks in block containersystem 402. Moreover, the use of a graph of logical extents to representa block container 405 is illustrative only. Block containers 405 may berepresented using any suitable architecture, including any of the otherillustrative architectures described herein.

The use of block containers 405 to represent data instances in datastore 408 may provide flexibility for the storage and management of thedata instances. For example, for certain data storage services, datainstances can be any size and can be resized by reconfiguring the blockcontainers 405 representing the data instances. As another example,additional resources of block container system 402 may be used, such asby applying the resources to the block containers 405 to perform one ormore operations on the data instances. To illustrate, data reductionresources, data replication resources (e.g., snapshotting), and/orstorage reclamation resources of block container system 402 may beapplied to the data instances represented by block containers 405. Suchapplications may provide instantaneous and/or efficient snapshotting ofthe data instances in data store 408, reducing of data by using multipleblock containers 405 to point to the same stored content that areassociated with multiple data instances, and garbage collecting toreclaim storage in data store 408.

Block containers 405 of block container system 402 may be adapted forrepresenting and managing data in data store 408. For example, anarchitecture used to represent a block container 405 may be adapted toreduce or minimize overhead that is associated with the block container405. To illustrate, a block container 405 may be associated with avolume in a block storage service such that the block container 405 istied to an overhead associated with the volume. The block container 405or another block container 405 may be adapted by freeing it from thevolume and/or at least some of the overhead associated with the volume.For example, overhead such as metadata overhead, administrativeoverhead, visual overhead, representation overhead associated withpresented, user managed structures, and/or overhead associated with hostexports may be reduced or for some types of overhead eliminated from theblock container system 402. For example, block containers 405 may bepresented to and/or otherwise used by one or more storage serviceswithout being presented to or in any way directly used by users of thestorage services and/or without being exported or otherwise exposedexternally on an individual basis. Such configurations may allow blockcontainers 405 to have minimal overhead in block container system 402,and in some cases to have none of one or more of the types of overheadsmentioned above. For example, a storage service such as a file storageservice may present a file system as a whole, as an exported and useradministered entity. These features may allow a data instance to berepresented with a block container 405 that has substantially lessoverhead in comparison with, say, a set of block devices which areimplemented using similar internal structure as the described blockcontainer. Accordingly, for the same finite physical storage resources,container utilization system 404 may store and manage many more datainstances represented with block containers 405 compared to the numberof volumes that can be represented in block container system 402. Incertain examples, for instance, only tens of thousands of volumes may bepractically represented using full administrative load volumesimplemented in the style of block containers 405 compared to practicalsupport for billions of data instances being represented using adapted,low administrative load block containers 405.

Container utilization system 404 may be configured to perform one ormore operations to provide data store 408 and to represent and managedata in data store 408 using block containers 405 and resources 406 ofblock container system 402. Such operations may include, withoutlimitation, writing data, reading data, creating a data instance,setting a length of a data instance, retrieving information about data,deleting data, snapshotting data, appending data, reducing data,replicating data, and reclaiming storage in data store 408. In certainexamples, garbage collection resources and/or other resources of blockcontainer system 402 may be scaled to handle large numbers of datainstances represented with block containers 405.

In certain examples, block containers 405 can provide identifiers formedof multiple parts that may include, for example, a namespace part and aunique identifier within the context of the namespace, where differentparts of the identifiers might be provided by varying combinations ofthe layer implementing the block containers 405 and the layer requestingthat block containers 405 be created. Snapshots, clones, checkpoints,and replicas can form new block container names such that some parts areretained while others are adjusted in a common way, such as by retainingsome unique identifier associated with a particular block containerwhile including a common substring representing the snapshot, clone,checkpoint, or replica. So, for example, given a file storage systembuilt from block containers 405 named using a combination of a filesystem name or identifier and a block container identifier that isunique relative to the file system, when making a clone of the filestorage system's files, directories, and other data and metadata, thecloned block containers 405 can retain their file system relative uniqueidentifiers while adjusting the file storage system identifier part tobe an identifier for the file storage system clone. Then, file storagesystem or other storage service logic can be pointed at the cloned blockcontainers 405 based on the name pattern of the file storage systemclone while reusing the unique identifier parts of the block containernames to match the block containers 405 to the logical components withinthe file storage system.

Alternately, or additionally, block containers 405 can be grouped invarious ways such that block containers 405 have names (including namesthat are simple, dynamically assigned integers) within some group. Insuch a case, a file storage system or other storage service may be builtto make use of one or more groups, such that making a snapshot or cloneof a group results in a new group that retains the block container namesbut has a different group name or identifier. In this case, storageservice logic can be pointed at a group instead of utilizing some othernaming pattern of block containers 405.

In certain examples, such groups may be based on pods, or for apod-based storage system, groups or other types of block containercollections can be contained within pods. Pods may provide a convenientscheme for additional forms of snapshots, clones, replication schemes,symmetric synchronous replication, continuous data protection, and more.

Container utilization system 404 may provide an application programinterface (API) 410 as shown in FIG. 4B. API 410 may include a set ofdefined operations that may be performed by container utilization system404 when the operations are called. The set of operations may includeand/or support any of the operations of container utilization system 404described herein. As shown in FIG. 4B, API 410 may be communicativelycoupled to data store 408 and block containers 405. Accordingly, API 410may perform operations on block containers 405 of block container system402. In certain examples, API 410 may perform operations on blockcontainers 405 by invoking and applying one or more resources 406 (e.g.,defined functions) of block container system 402 to perform operationsdescribed herein. API 410 may also perform operations on data store 408and data stored in data store 408.

API 410 may be exposed to and used by one or more data storage services.In such a configuration, the data storage services may leverage andbenefit from one or more features of data storage system 400. Forexample, the data storage services may directly leverage and benefitfrom data storage provided by container utilization system 404 andindirectly leverage and benefit from block containers 405 and resources406 of block container system 402 that are used by container utilizationsystem 404.

FIG. 6A illustrates an example of a data storage system 600 thatincludes a data storage service 602 configured to interface withcontainer utilization system 404 by way of API 410. Data storage service602 may be implemented in any suitable way (e.g., as a data storagesystem, as an engine, as a virtual data system, etc.) and may interfacewith container utilization system 404 in any suitable way, including byissuing calls to and receiving responses to the calls from API 410 ofcontainer utilization system 404.

Data storage service 602 may be any suitable type of data storageservice, such as a file storage service that uses one or more filestorage protocols, an object storage service that uses one or moreobject storage protocols, a block storage service that uses one or moreblock storage protocols, a database service that uses one or moredatabase protocols, etc. In certain examples, data storage service 602is a data storage service 602 that is not a block storage service.

Data storage system 400 and/or data storage system 600 may provide datastorage service 602 with access to resources of block container system402 and container utilization system 404 (e.g., through API 410) suchthat data storage service 602 may be built on block containers 405. Forexample, data storage service 602 may store and manage content of datastorage service 602 in data store 408, and the content may be stored andmanaged using block containers 405 as described herein.

An example in which data storage service 602 is a file storage servicewill now be described. The example is illustrative. A file storageservice may be implemented in other ways in other examples. Data storageservice 602 may be a different type of data storage service in yet otherexamples.

In certain implementations, data storage service 602 may include avirtual file system (VFS) configured to manage file data. For example,the VFS may manage metadata that represents information about data filesand how the data files map to data instances such as block containersstored in data store 408. In certain embodiments, the VFS may employdata structures called envelopes in which metadata about the data filesand mappings of the data files to block containers is maintained. Anenvelope may include information about one or more data files. Envelopesmay include any suitable information about data files and correspondingblock containers, including, file identifiers, block containeridentifiers, container store map information (e.g., info aboutrelationships between file identifiers and block container identifiers),snapshot info for the data (indicating older block container versions),root node identifiers for root nodes of graphs representing blockcontainers in container-based data store 408, size information forfiles, block containers, and/or graphs of logical extents, statisticsfor the data, log information for the data, and the like. In someexamples, envelopes may be directories plus caches of metadata aboutfiles contained in the directories. Data storage service 602 may beconfigured to provide any information about data files, including blockcontainer identifiers and/or other information represented in envelopes,to API 410 in conjunction with calling functions of API 410. Datastorage service 602 may also be configured to receive information aboutdata files, including block container identifiers and/or otherinformation to be represented in envelopes (e.g., logical size of afile, logical space used for the file, etc.), from API 410 inconjunction with responses from called functions of API 410.

In certain implementations, data storage service 602 may be configuredto generate and provide block container identifiers for use by containerutilization system 404. Container utilization system 404 may beconfigured to use the block container identifiers as local identifierswithin container utilization system 404 or may be configured to map theblock container identifiers to local identifiers generated and usedwithin container utilization system 404.

In certain embodiments, data storage service 602 and containerutilization system 404 may be configured to represent each data file orenvelope as a block container in data store 408. Data storage service602 may be configured to cache files and push cached block containers tocontainer utilization system 404 in batches for writing to data store408. Data store 408, in turn, may persist block containers andassociated versions (e.g., snapshots) and make the block containersavailable for fast access by data storage service 602.

Container utilization system 404 may be configured to providetransaction semantics for use by data storage service 602. In certainembodiments, the transaction semantics may allow, for at least someclasses of operations, data storage service 602 to issue multipleupdates to a file and request that all or none of the updates be made tothe block container representing the file. Container utilization system404 may be configured to implement all or none of the updates and returneither new or old data to data storage service 602.

In certain implementations, container utilization system 404 and datastorage service 602 may be configured to support multi-containertransactions. For example, container utilization system 404 may use oneor more resources 406 of block container system 402 to provide an arrayof parallel transaction queues (e.g., 32 buffers) that can be written toindependently for increased throughput. The number of paralleltransaction queues written to may be maximized to increase throughput.

To illustrate the use of such parallel transaction queues, atransactional update may include data for multiple metadata elementsand/or operations (e.g., create a block container, create another blockcontainer, append to a block container, etc.). Container utilizationsystem 404 may be configured to perform everything associated with sucha transactional update all together or not at all. Accordingly,everything in the transactional update may be made visible to a host atthe same time.

Data storage service 602 may be configured to provide file storageservices (e.g., to a host server that is not shown in FIG. 6A). To thisend, data storage service 602 may be configured to support anyfile-based storage protocols, including for example, NFS, SMB, and/orCIFS. One or more such protocols may be used by a host server, forexample, to interface with the VFS.

In the case of a storage system providing a file service, such asthrough NFS or SMB, container utilization system 404 makes it verysimple for the file service layer to concentrate on protocol handlingand file service semantics without being concerned about layout outfiles on the storage, while benefiting from the rich semantics of blockcontainers 405. For example, file stores get the benefit ofdeduplication and compression without having to implement those featuresseparately, will also benefit from all the other block container or podservices such as snapshots, clones and various types, forms, and methodsof replication, and may be able to leverage symmetric synchronousreplication to provide symmetrically accessible mirrored files in asimple fashion. Individual files can be cloned easily by virtuallycopying one block container to another as part of creating a new file. Afile can be re-cloned by virtually copying the block containerassociated with the first file to the block container associated withthe second container. This can, for example, make it very fast and spaceefficient to copy a collection of virtual machine images stored asfiles, or for storing Docker- and Kubernetes-style containers which aregenerally stored as a collection of overlay directories but wherecloning operations could be used to eliminate the separate overhead ofreading and writing to these overlays during run-time operation of sucha container

In certain examples, a file system of a file storage service can beversioned by making a sequence of snapshots of the file system'sassociated block containers based on naming or grouping rules. Ifsubtrees of a file system are differentiated in a coordinated way suchas with attributes of block containers, for example based on variouskinds of tags or name components, then a file system can leverage thatto get highly performant and flexible subdirectory snapshots throughrequests to the block container service layer to snapshot blockcontainers with those attributes to create new block containers with aparticular set of new attributes to differentiate them from the originalblock containers.

While an example of a file storage service system interfacing withcontainer utilization system 404 has been described above, any suitabledata storage service system, including another type of data storageservice system, may interface with container utilization system 404. Forexample, an object-based storage service system (e.g., an S3 storageservice system) may interface with container utilization system 404. Anobject store may get the benefit of deduplication and compressionwithout having to implement those features separately, may also benefitfrom all the other block container or pod services, and may even be ableto leverage symmetric synchronous replication to provide symmetricallyaccessible mirrored objects in a simple fashion. Individual objects canbe cloned easily by virtually copying one block container to another aspart of creating a new object. An object can be re-cloned by virtuallycopying the block container associated with the first object to theblock container associated with the second container. This can, forexample, make it very fast and space efficient to copy a collection ofvirtual machine images or containers. As another example, a databaseservice system may interface with container utilization system 404. Adatabase that stores blobs may benefit from deduplication and/or inheritadditional block container and pod capabilities.

A storage service system that interfaces with container utilizationsystem 404 may be configured to provide data storage services using anysuitable data storage protocol or set of protocols.

While FIG. 6A illustrates one data storage service 602 supported bycontainer utilization system 404 and block container system 402, thesesystems may be configured to support any number of data storageservices, including data storage services of different types. FIG. 6Billustrates an example of a data storage system 604 that includes Nnumber of data storage services 602 (data storage services 602-1 through602-N) configured to interface with container utilization system 404 byway of API 410. The plurality of data storage services 602 shown in FIG.6B may include any suitable combination of data storage services (e.g.,file, block, object, database, etc.) configured to interface withcontainer utilization system 404 by way of API 410.

Data storage services 602 may be provided with access to resources ofblock container system 402 and container utilization system 404 (e.g.,through API 410) such that data storage services 602 may be built onblock containers 405. For example, data storage services 602 may storeand manage content of data storage services 602 in one or more datastores (e.g., data store 408) maintained by container utilization system404, and the content may be stored and managed using block containers405 as described herein.

Container utilization system 404 may function as an intermediary betweenblock container system 402 and one or more data storage services 602.This may allow different data storage services 602 to easily interfacewith container utilization system 404 (e.g., by way of API 410) in orderto benefit from block containers 405 and resources 406 of blockcontainer system 402.

In certain examples, block container system 402 and/or containerutilization system 404 may be configured to allow space efficientvirtual copying or cloning of block ranges or block containersassociated with one storage service to be used by another storageservice. As example, individual files or sets of files of one filesystem may be virtually copied to another file system. As anotherexample, individual files or sets of files of a file system may beturned into individual objects or sets of objects in an object store (orvice versa). As another example, a database blob may be virtually copiedfrom a database to make a file or object. In a more complex example, afile contained within a virtual machine's file system image where thefile system image is itself stored, for example, as either a blockvolume or an individual file on a block container, could be virtuallycopied to form an independent file or object within a file system orobject store that directly utilizes block containers.

In certain examples, block container system 402 and/or containerutilization system 404 may be configured to provide a variant of this inwhich multiple identities may be provided for a block container suchthat different storage service can share a block container, whichsharing may include inheriting changes to the content of the blockcontainer. For example, a file system and an object store may share ablock container. The file system may use a first identifier for theblock container, and the object store may use a second identifier forthe block container. Changes made to content of a file in the filesystem may be inherited by a corresponding object in the object store byway of the changes to the content of the file being made in the sharedblock container.

While FIGS. 4A, 4B, 6A, and 6B illustrate container utilization system404 and block container system 402 as separate entities, otherconfigurations may be implemented in other embodiments. As an example,container utilization system 404 and block container system 402 may beflattened into a container storage system configured to operate in anyof the ways described herein. This may be accomplished in any suitableway, including by implementing one or more of resources 406 in acontainer storage system. The resources 406 implemented in the containerstorage system may include the same resources as may be used in a blockstorage system and/or may include adaptations of the resources that areconfigured for use with the container storage system. The reader willappreciate that any other implementation of a container storage systemmay be configured to operate in any of the ways described herein usingany of the illustrative resources described herein and/or other suitableresource.

FIG. 7 illustrates an exemplary method 700 for a data storage system.While FIG. 7 illustrates exemplary operations according to oneembodiment, other embodiments may omit, add to, reorder, and/or modifyany of the operations shown in FIG. 7. One or more of the operationsshown in FIG. 7 may be performed by data storage system 400, anycomponents included therein, and/or any implementation thereof.

In operation 702, block containers are provided. For example, blockcontainer system 402 may provide block containers 405 in any of the waysdescribed herein.

In operation 704, the block containers are used to store content for oneor more data storage services. For example, container utilization system404 may use block containers 405 to store content for one or more datastorage services 602 in any of the ways described herein.

In operation 706, the content stored with the block containers ismanaged. For example, block container system 402 and/or containerutilization system 404 may perform one or more operations to manage thecontent, such as by applying resources 406 of block container system 402to perform snapshotting, cloning, deduplication, compression, garbagecollection, and/or other operations on the content stored with blockcontainers 405.

FIG. 8 illustrates an exemplary method 800 for writing and managingdata. While FIG. 8 illustrates exemplary operations according to oneembodiment, other embodiments may omit, add to, reorder, and/or modifyany of the operations shown in FIG. 8. One or more of the operationsshown in FIG. 8 may be performed by data storage system 400, anycomponents included therein, and/or any implementation thereof.

In operation 802, a data storage system receives a request to writedata. The data storage system may receive the request from any suitablesource, such as a data storage service 602, another data storage systemconfigured to interface with the data storage system, or a host (e.g., ahost controller, a host server, etc.).

The request may include any information indicating or associated withthe request. For example, the request may include data to be written andinformation about the data, such as a data identifier (a data fileidentifier, a block container identifier to be used by the data storagesystem to identify a block container to which the data is written), sizeinformation for the data, etc. Data fields included in the request mayby defined by a schema used to interface with the data storage system.

In operation 804, the data storage system stores the data to a datastore in response to the request received in operation 802. The datastorage system may use one or more block containers to store the data tothe data store.

Operation 804 may include the data storage system performing one or moreprocesses to store the data to the data store. The processes may use anyof the illustrative resources described herein. In certain examples, thestoring of the data to the data store may include multi-stage processessuch as a frontend process and a backend process. The frontend processmay include use of resources to write the data to a temporary data store(e.g., a non-volatile data store, NVRAM, a cache, etc.) and reducing thedata (e.g., via pattern recognition, data deduplication, and compressingthe data). The frontend process may be performed inline such that thedata storage system may notify, with low latency, a host from which therequest was received that the data write has been performed. The backendprocess may include use of resources to write the data to the datastore, which may include batch writing the reduced data to all-flashmemory.

In operation 806, the data storage system manages the data in the datastore using one or more resources associated with the block containers.Operation 806 may include the data storage system performing one or moreprocesses to use one or more resources of block container system 402 tomanage the data in the data store. The processes may use any of theillustrative resources described herein. In certain examples, themanaging of the data in the data store may include using resources ofblock container system 402 to reduce the data in the data store (e.g.,by deep deduplication, deep compression, etc.) and/or reclaim storage(e.g., by garbage collection).

FIG. 9 illustrates an exemplary method 900 for reading data. While FIG.9 illustrates exemplary operations according to one embodiment, otherembodiments may omit, add to, reorder, and/or modify any of theoperations shown in FIG. 9. One or more of the operations shown in FIG.9 may be performed by data storage system 400, any components includedtherein, and/or any implementation thereof.

In operation 902, a data storage system receives a request to read data.The data storage system may receive the request from any suitablesource, such as data storage service 602, another data storage systemconfigured to interface with the data storage system, or a host (e.g., ahost controller, a host server, etc.).

The request may include any information indicating or associated withthe data to be read. For example, the request may include informationabout the data to be read, such as a data identifier (a data fileidentifier, a data object identifier used by the data storage system toidentify a data object in which the object data is stored, etc.). Datafields included in the request may by defined by a schema used tointerface with the data storage system.

In operation 904, the data storage system retrieves the data from thedata store in response to the request received in operation 902. Thecontainer storage system may use one or more block containers toretrieve the data from the data store. For example, the data storagesystem may use a block container that represents the data in the datastore, to locate and retrieve the data. This may include using a dataidentifier to identify a handle of the block container and using thehandle to access and use the block container to locate and retrieve thedata.

Additionally, in certain examples, the data storage system may use alookaside data structure, such as a lookaside table or cache, to locateand retrieve the data. The data storage system may be configured togenerate and populate the lookaside data structure with datarepresenting a log of actions that are to be performed by the datastorage system in a time-shifted manner, such as later as part of abackground process. For example, the lookaside data structure mayindicate tuples that are written to a silo but not yet written to thedata store. Accordingly, the data storage system may use the lookasidedata structure, together with a block container, to locate and retrievedata being read.

FIG. 10 illustrates an exemplary method 1000 for using a block containerto represent data in a data store. While FIG. 10 illustrates exemplaryoperations according to one embodiment, other embodiments may omit, addto, reorder, and/or modify any of the operations shown in FIG. 10. Oneor more of the operations shown in FIG. 10 may be performed by a datastorage system, any components included therein, and/or anyimplementation thereof.

In operation 1002, a data storage system receives a request to writedata to a data store. The data storage system may receive the requestfrom any suitable source, such as a data storage service 602, anotherdata storage system configured to interface with the data storagesystem, or a host (e.g., a host controller, a host server, etc.).

The request may include any information indicating or associated withthe request. For example, the request may include data to be written andinformation about the data, such as a data identifier (a data fileidentifier, a data object identifier to be used by the data storagesystem to identify a data instance to which the data is written), sizeinformation for the data, etc. Data fields included in the request mayby defined by a schema used to interface with the data storage system.

In operation 1004, the data storage system uses a block container tostore the data to the data store in response to the request received inoperation 1002. The data storage system uses a handle having a uniqueidentifier mapped to the block container to identify the blockcontainer.

In certain examples, the storing of the data to the data store mayinclude the data storage system performing multi-stage processes such asa frontend process and a backend process. The frontend process mayinclude writing the data to a temporary data store (e.g., a non-volatiledata store, NVRAM, a cache, etc.) and reducing the data (e.g., viapattern recognition, data deduplication, and compressing the data). Thefrontend process may be performed inline such that the data storagesystem may notify a host, with low latency, that the data write has beenperformed. The backend process may include writing the data to the datastore, which may include batch writing the reduced data to all-flashmemory.

In operation 1006, the data storage system receives a request to readthe data from the data store. The data storage system may receive therequest from any suitable source, such as a data storage service 602,another data storage system configured to interface with the containerstorage system, or a host (e.g., a host controller, a host server,etc.).

The request may include any information indicating or associated withthe data to be read. For example, the request may include informationabout the data to be read, such as a data identifier (a data fileidentifier, a data object identifier used by the data storage system toidentify a data object in which the data is stored, etc.). Data fieldsincluded in the request may by defined by a schema used to interfacewith the data storage system.

In operation 1008, the data storage system retrieves the data from thedata store using the handle. This may include using the handle toidentify and use the block container to locate and retrieve the data.Operation 1008 may additionally include searching a lookaside datastructure to identify any data indicating that the block container is tobe used for retrieval of data (e.g., data from a snapshot of the datathat is not yet carried through to an updated version of the data).

FIG. 11 illustrates an exemplary method 1100 for using a block containerto represent data in a data store. While FIG. 11 illustrates exemplaryoperations according to one embodiment, other embodiments may omit, addto, reorder, and/or modify any of the operations shown in FIG. 11. Oneor more of the operations shown in FIG. 11 may be performed by a datastorage system, any components included therein, and/or anyimplementation thereof.

In operation 1102, a data storage system provides a block container(e.g., by thin provisioning the block container). Operation 1102, whichmay be performed in response to a request to write data to a data store,may be performed in any suitable way. For example, the data storagesystem may provision the block container based on data to be written tothe data store and/or further based on block containers that alreadyexist in the data store.

In operation 1104, the data storage system stores data representing adata instance to the block container. Operation 1104 may be performed inany suitable way, including by writing the data to logical and/orphysical storage media locations and associating the block container tothe logical storage media locations (e.g., logical addresses) mapped tothe physical storage media locations.

In operation 1106, the data storage system maps a unique identifier forthe data instance to a handle of the block container. Operation 1106 maybe performed in any suitable way, including by the data storage systemreceiving or generating the unique identifier for the data instance andassociating the unique identifier with the block container (e.g., bystoring the unique identifier in the block container).

In accordance with certain embodiments of the present disclosure, astorage system may establish and use path sets to coordinate operationsof the storage system. For example, path sets may be established andused to manage group operations in file storage, such as snapshotoperations to one or more particular directory trees (e.g., one or moredirectory trees of one or more managed directories) of a file storagesystem.

As used herein, path sets may represent collections of data storageentities that are included in groups to which group operations may beapplied. For example, a path set may represent a collection of datastorage entities that are included in a particular directory tree of afile storage system (e.g., data storage entities that are located at andbelow a particular directory of the file storage system). In commonusage, a path (or pathname) within a file system represents ahierarchical order of directories from the root directory of the filesystem to a particular file or directory and leading to the name andidentity of the particular file or directory within that file system. Apath set, then, may represent the set of all files or directories whosepaths (or pathnames) begin with a particular common path from the filesystem's root directory to a directory (within the hierarchy) on whichgroup operations described in this application can be performed.Examples of path sets are described in detail herein.

Path sets may be particularly useful in a storage system that includesseparate layers. For example, a storage system may have a service layerthat provides presentation aspects and a storage layer that providesstorage aspects that support the service layer. Such a configuration mayprovide one or more benefits to the storage system and/or users of thestorage system, such as a rich set of functions for managing datastorage at the storage layer. The service layer may apply operations atthe service layer. The storage system may establish and use path sets,which are visible to the storage layer, to coordinate implementation ofthose operations at the storage layer. For example, for group operationsthat are applied at the service layer, path sets may be established andused to selectively implement certain kinds of group operations (e.g.,snapshot operations), such as directory-tree granularity operations, atthe storage layer as needed and/or on a just-in-time basis, in a mannerthat efficiently utilizes resources of the storage system.

FIG. 12 illustrates an example of a data storage system 1200 (“storagesystem 1200”) that includes a service layer 1202 and a storage layer1204 communicatively coupled to one another. Service layer 1202 andstorage layer 1204 may be communicatively coupled to one another usingany suitable data communication technologies (e.g., middleware,application program interfaces, other interfaces, etc. of storage system1200).

Service layer 1202 may be configured to perform one or more operationsto provide a data storage service of storage system 1200. For example,service layer 1202 may provide one or more interfaces configured to beused by one or more devices external of storage system 1200 to accessand use the data storage service. Service layer 1202 may include orprovide a presentation layer configured to provide the interface(s)and/or the data storage service to external devices.

Service layer 1202 may be configured to manage service layer entities1204 for the presentation layer of storage system 1200. Service layerentities 1204 may include any type or types of data structures suitableto support the data storage service provided by service layer 1202. Forexample, the data storage service may include a file storage service,and service layer entities 1206 may include file storage entities suchas hierarchically arranged directories and files of a file system.Service layer 1202 may manage service layer entities 1204 in any waysuitable to provide the data storage service, including by creatingservice layer entities 1206 and applying operations to service layerentities 1206. Examples of operations that may be applied to servicelayer entities 1206 may include provisioning, writing to, reading from,modifying, moving (from one location in a directory hierarchy to anotherlocation in a directory hierarchy or between directory hierarchies),copying, grouping, organizing, protecting, versioning, snapshotting,cloning, replicating, deleting, and otherwise operating on service layerentities 1206 in the service layer 1202.

While service layer 1202 may manage service layer entities 1206 andprovide the presentation layer service of storage system 1200, storagelayer 1204 may be configured to perform operations to implement certainaspects of the service layer 1202, such as the service layer entities1206 and operations applied to the service layer entities 1206 by theservice layer 1202. In this regard, the service layer 1202 may beseparated from certain implementation aspects of the service layer 1202because storage layer 1204 is configured to perform those implementationaspects, which may include storing data and metadata for the servicelayer entities 1206. To this end, service layer 1202 may provide, tostorage layer 1204, information about service layer entities 1206 and/oroperations performed by service layer 1202. Storage layer 1204 mayreceive the information and, based on the information, performimplementation operations to implement the operations of the servicelayer 1202 at the storage layer 1204.

Storage layer 1204 may be configured to create and manage storage layerentities 1208 that are associated with service layer entities 1206. Thestorage layer entities 1208 may represent the service layer entities1206 in any suitable way, such as by storing data representative of theservice layer entities 1206 (e.g., data and metadata of the servicelayer entities 1206). The storage layer entities 1208 may include anytype or types of data entities suitable to represent the service layerentities 1206. In certain examples, storage layer entities 1208 includedata structures arranged in a flat or non-hierarchical configuration, orwith minimal hierarchy such as collections of collections of storagelayer entities 1208. Accordingly, a hierarchical configuration ofservice layer entities 1206 may not be reflected in storage layerentities 1208. In certain examples, storage layer entities 1208 includeblock objects, which are described herein.

The separation of operations of storage system 1200 into service layer1202 operations and storage layer 1204 operations, and/or the use ofstorage layer entities 1208 to represent service layer entities 1206 mayprovide one or more benefits to storage system 1200. For example,storage layer 1204 may provide flexibility in implementing operations ondata, managing data, and using resources of storage system 1200.Additionally or alternatively, storage layer 1204 may provide datastructures (e.g., storage layer entities 1208) and/or data storagemanagement operations that would be difficult, impractical, lessefficient, or more resource intensive to implement in service layer1202. In certain examples, such operations of storage layer 1204 may befacilitated by use of block objects as storage layer entities 1208,which block objects may provide any of the features and/or benefits ofblock objects as described herein.

As mentioned, when service layer 1202 applies operations to servicelayer entities 1206, service layer 1202 may communicate informationabout the operations to storage layer 1204. The information may beprovided in any suitable form, including as one or more requests (e.g.,application program interface calls) or requests through a network(e.g., a remote procedure call) to implement aspects of the servicelayer operations within the storage layer 1204. Storage layer 1204 maybe configured to implement the operations on corresponding storage layerentities 1208 in any suitable way. In certain examples and/or forcertain operations, storage layer 1204 may implement the operations inreal time as information about the operations is received from servicelayer 1202. For certain other examples and/or operations, storage layer1204 may selectively perform and/or delay performing the operationsuntil performing the operation becomes necessary, or more efficient,and/or in response to certain defined events. Such delayed and/orselective performing of the operations on storage layer entities 1208may provide one or more benefits to storage system 1200. For example,the number of I/O operation requests to persistent storage or throughinternal I/O buses or other interconnects by storage system 1200 may bereduced. This may conserve resources and facilitate efficient operationof storage system 1200.

In examples in which implementation of operations to a particular groupof service layer entities (e.g., a directory tree of a manageddirectory) applied at the service layer 1204 is delayed or is selectiveat storage layer 1204, maintaining consistency of data between servicelayer 1202 and storage layer 1204 may be a challenge at least becauseduring periods between application of operations to service layerentities 1206 at the service layer 1202 and implementation of theoperations on storage layer entities 1208 at the storage layer 1204,additional operations may be applied to service layer entities 1206 atthe service layer 1202. The additional operations may alter the servicelayer entities 1206, such as by changing a hierarchical configuration ofservice layer entities 1206. Subsequently, when storage layer 1204determines to delay operations on storage layer entities 1208 (e.g., fora “lazy” implementation in which performance of certain group operationsare intentionally delayed and then selectively implemented on individualentities associated with a group when operating on the entities for someother reason such as modifying the entities), in order to maintainconsistency of data with service layer 1202, storage layer 1204 shouldimplement the operations on storage layer entities 1208 that areassociated with service layer entities 1206 at the time the operationswere applied to service layer entities 1206, as the service layerentities 1206 existed before the additional operations changed thehierarchical configuration of service layer entities 1206.

Another challenge in maintaining data consistency between service layer1202 and storage layer 1204 is that certain information maintained bythe service layer 1202 may not be maintained by the storage layer 1204.In certain examples, service layer 1202 may maintain information aboutconfigurations of service layer entities 1206, such as information aboutgroupings of service layer entities 1206 in service layer 1202. Anexample of such a grouping is a set of all service layer entities 1206within a hierarchical configuration such as a directory hierarchy.Service layer 1202 may maintain information about any other type ortypes of groupings of service layer entities 1206 and/or relationshipsbetween the service layer entities 1206. Such hierarchy detailinformation about the relationships between the service layer entities1206 in a directory hierarchy may not be known to the storage layer1204. While this may provide certain benefits for storage layer 1204, itmay also present a challenge to maintaining data consistency betweenstorage layer 1204 and service layer 1202, particularly whenimplementation of operations applied to groups of service layer entities1206 in service layer 1202 is intentionally delayed in storage layer1204.

Storage system 1200 may establish and use path sets 1210 to coordinateimplementation of operations on storage layer entities 1208. Forexample, storage system 1200 may establish and use path sets 1210 tomanage storage layer implementation of service layer operations appliedin service layer 1202. To illustrate, an operation may be applied to adirectory tree (e.g., to all service layer entities 1208 that areorganized within a particular directory and the tree of directoriesbelow that directory) of a file system in service layer 1202. Storagelayer 1204 may use path sets 1210 to manage implementation of theoperation in storage layer 1204, including by using path sets 1210 toidentify relationships between storage layer entities 1208 and theoperation.

Path sets 1210 may be managed by any suitable component of storagesystem 1200. For example, path sets 1210 may be managed by service layer1202, storage layer 1204, an intermediate layer between service layer1202 and storage layer 1204, or any combination of layers of storagesystem 1200. Path sets 1210 may be represented using any suitableidentifiable data structures, such as data objects or any otheridentifiable construct.

Path sets 1210 may represent relationships between certain service layerentities 1206 and storage layer entities 1208 associated with (e.g.,that implement) those service layer entities 1206. For example, incertain embodiments path sets 1210 may represent collections of storagelayer entities 1208 associated with service layer entities 1206 of adirectory hierarchy of a file system managed by service layer 1202. Forinstance, an illustrative path set 1210 may represent a collection ofstorage layer entities 1208 that are associated with, or reside within,a directory tree at and below a particular directory of a file systemmanaged by service layer 1202, or more specifically a collection ofstorage layer entities 1208 that correspond to files and directoriesincluded directly or indirectly through hierarchical inclusion withinthe directory of the file system.

Such a path set 1210 may represent the collection of storage layerentities 1208 associated with the directory without representing orincluding information about the hierarchical relationships between thefiles and directories in the directory of the file system. That is, thepath set 1210 may be unaware of the hierarchical relationships betweenthe files and directories in the directory in the service layer 1202.The path set 1210 may simply represent that the collection of storagelayer entities 1208 is associated with the directory withoutrepresenting or being aware of hierarchical relationships between thefiles and directories within the directory. Accordingly, the files anddirectories can be moved around and linked within the directory, therebychanging their hierarchical relationships within the directory, and thepath set 1210 may remain unchanged and continue to represent that thecollection of storage layer entities 1208 is associated with thedirectory. In this or any other suitable way, a path set 1210 mayassociate storage layer entities 1208 in storage layer 1204 with adirectory in service layer 1202, without having to record or understandall of the hierarchical relationships between the files and directoriesin the directory in service layer 1202.

A path set 1210 may be associated with a grouping of service layerentities 1206, such as a directory of files and directories, in anysuitable way. For example, service layer 1202 may manage informationthat links a directory to a path set 1210 for the directory. In certainexamples, a directory of a file system managed by the service layer 1202may include metadata pointing to the path set 1210 associated with thedirectory.

A path set 1210 may be associated with a collection of storage layerentities 1208 in any suitable way. For example, storage layer 1204 maymanage information that links storage layer entities 1208 to a path set1210, such as a path set of a directory that includes files anddirectories that are represented by the storage layer entities 1208 instorage layer 1204. In certain examples, storage layer entities 1208 mayinclude metadata pointing the storage layer entities 1208 to the pathset 1210.

As mentioned, the path set 1210 may include information representing anassociation between the directory in the service layer 1202 and acollection of storage layer entities 1208 that represent the files anddirectories of the directory in the storage layer 1204. The path set1210 may include additional information about the directory, such asinformation about operations (e.g., snapshots) applied at the directoryand all of its hierarchical constituents in the service layer 1202,versions of the operations and/or the path set 1210, etc. The path set1210 may be any suitable identifiable construct that is associated withthe directory and that is known to (e.g., implemented by) the storagelayer 1204 or an intermediate layer between the service layer 1202 andthe storage layer 1204. Illustrative examples of path sets 1210 will nowbe described.

FIG. 13A illustrates an example of a path set that may be establishedand used by storage system 1200. FIG. 13A illustrates an example pathset 1300 that represents a relationship between service layer entities(SVEs) 1302 of a service layer and storage layer entities (SGEs) 1304that represent the SVEs 1302 in a storage layer. As shown, the SVEs 1302may include SVE1, SVE2, SVE3, and SVE4 arranged in a hierarchicalconfiguration such as a directory hierarchy. SVEs 1302 may be in adirectory hierarchy having SVE1 as the top node, SVE2 and SVE4 aschildren nodes of SVE1, and SVE3 as a child node of SVE2. Thus, SVE1 maybe said to be a directory that includes SVE2, SVE3, and SVE4 in itsdirectory tree. The SGEs 1304 may include SGE1, SGE2, SGE3, and SGE4that represent the SVEs 1302 that are included in the directory tree ofSVE1. Thus, SGEs 1304 are a collection of SGEs 1304 associated withSVE1.

Path set 1300 may indicate that the collection of SGEs 1304 (SGE1, SGE2,SGE3, and SGE4) are associated with the directory tree of SVE1 byindicating that the collection of SGEs 1304 are associated with SVE1(the top node of the directory tree). In this or a similar manner, pathset 1300 may not represent an entire hierarchical structure of an entirefile system, but may simply associate the collection of SGEs 1304 to thedirectory tree (by associating SGEs 1304 to the top node of thedirectory tree). The path set 1300 may simply associate the collectionof SGEs 1304 to the directory tree without representing relationshipsbetween the SGEs 1304.

Path set 1300 may indicate a relationship between SVE1 and SGEs 1304 inany suitable way. As an example, path set 1300 may include information(e.g., metadata) pointing to SVE1 and SGEs 1304. Such a configuration isrepresented by a configuration of arrows 1306 in FIG. 13A. As anotherexample, SVE1 and SGEs 1304 may include information (e.g., metadata)pointing to path set 1300. Such a configuration is represented by aconfiguration of arrows 1312 in FIG. 13B.

While path set 1300 shown in FIGS. 13A and 13B illustrates an example ofa path set, path sets may be configured in any suitable way to representrelationships between storage layer entities and service layer entities.For example, path sets may be established and maintained for storagelayer entities and may indicate certain information about relationshipsof the storage layer entities to certain service layer entities (e.g.,managed directories). Such path sets may be referred to as entity-levelpath sets.

FIG. 13C illustrates an example of entity-level path sets that may beestablished and used by storage system 1200. FIG. 13C illustratesexample path sets 1310 associated with storage layer entities (SGEs)1304 that represent service layer entities (SVEs) 1302. One or more ofSVEs 1302 may each be assigned a path identifier. The path identifiersmay be used to define path sets 1310 that indicate relationships of SGEs1304 to SVEs 1302 that are assigned path identifiers.

For example, the SVEs 1302 may include SVE1, SVE2, SVE3, and SVE4arranged in a hierarchical configuration such as a directory hierarchy,as shown. Path identifiers may be assigned to SVE1 and SVE2. Toillustrate, the path identifier for SVE1 may be “SVE1,” and the pathidentifier for SVE2 may be “SVE2.” Path identifiers may be selectivelyassigned to service layer entities based on any criteria, logic, ordesignation. For instance, path identifiers may be assigned to SVE1 andSVE2 based on SVE1 and SVE2 being designated service layer entities foruse with path sets and/or certain operations (e.g., snapshotoperations). In certain examples, SVE1 and SVE2 may be designated asmanaged directories of a file system, and SVE3 and SVE4 may be filestorage elements other than elements that are designated to be manageddirectories. Accordingly, path identifiers may be assigned to SVE1 andSVE2 but not to SVE3 or SVE4.

The SGEs 1304 may include SGE1, SGE2, SGE3, and SGE4 that represent theSVEs 1302. Path sets 1310 may include a path set corresponding to eachof the SGEs 1304. Each of the path sets 1310 may include informationabout certain SVEs 1302 that are associated with the respective SGE1304. For example, a path set for SGE1 indicates that SGE1 is includedin a directory tree of SVE1. In this case, SGE1 represents SVE1, whichis part of its own directory tree. A path set for SGE2 indicates thatSGE2 is in directory trees of SVE1 and SVE2. In this case, SGE2represents SVE2, which is part of its own directory tree and thedirectory tree of SVE1. A path set for SGE3 indicates that SGE3 is indirectory trees of SVE1 and SVE2. In this case, SGE3 represents SVE3,which is part of the directory tree of SVE1 and the directory tree ofSVE2. A path set for SGE4 indicates that SGE4 is in the directory treeof SVE1. In this case, SGE4 represents SVE4, which is part of thedirectory tree of SVE1. SVE3 and SVE4 may not be considered to part oftheir own directory trees for one or more reasons, such as SVE3 and SVE4being service layer entities other than a managed directory (e.g., astorage element such as a file or other non-directory data elementand/or directory data element that is not designated for use with pathset operations).

Storage system 1200 may be configured to establish and maintainentity-level path sets such as path sets 1310 in any suitable way. Forexample, storage system 1200 may establish path sets for storage layerentities when the storage layer entities are created and may dynamicallyupdate the path sets when configurations of service layer entitiesimplemented by the storage layer entities change in a way that moves theservice layer entities in and out of directories associated with pathsets 1310 (which changes in the service layer 1202 may cause storagelayer 1204 to update metadata for the storage layer entities). Storagesystem 1200 may be configured to manage path sets by tracking anychanges to hierarchical configurations that affect path set informationabout the hierarchical configurations and updating the path setsaccordingly (e.g., by detecting moves, hard links, etc.). Accordingly,when a service layer entity 1206 is moved between directories, a pathset of a storage layer entity 1208 that represents the service layerentity 1206 may be updated to reflect the move when the move changes thepath set. However, if the move is within a directory associated with apath set, or between directories associated with the same list ofmanaged directories, the move does not change the path set because theservice layer entity stayed within the managed directories, and so thepath set relationships need not be updated.

Path sets 1300 and 1310 are illustrative. Storage system 1200 may beconfigured to use other suitable implementations of path sets in otherembodiments.

Path sets may include additional information. For example, path sets mayinclude information about operations applied to groups of service layerentities 1206 in service layer 1202 of storage system 1200. Forinstance, when certain operations are applied to the contents of amanaged directory by service layer 1202, service layer 1202 may provideinformation about those operations for inclusion in a path setassociated with the managed directory. Such information may identify theoperations and the timing and/or sequence of those operations.

Path sets may be versioned. In certain examples, for instance, a pathset that is associated with a service layer entity and may represent oneversion of a path set within a set of path sets associated with theservice layer entity. For example, storage system 1200 may be configuredto establish versions of path sets for a managed directory based onoperations applied to the managed directory. One path set in the pathsets for the managed directory may represent an operation applied to themanaged directory at a particular time or within a temporal sequence ofoperations applied to the managed directory. Versions of path setsassociated with a service layer entity such as a managed directory maybe indexed in any suitable way, such as by increasing and applying aversion counter to a newly created path set. Examples of versioned pathsets and use of versioned path sets to coordinate implementation ofoperations on storage layer entities are described herein.

Examples of a storage system in which service layer 1202 includes a fileservice layer configured to provide a file storage service (such as anyfile storage service described herein or another suitable file storageservice) and in which storage layer 1204 includes a block object layerconfigured to manage block objects that implement aspects of the filestorage service (e.g., that implement service layer entities of the filestorage service) will now be described. Examples of path sets beingestablish and used will then be described in the context ofconfigurations in which a file storage service is implemented with blockobjects. One or more aspects of such example configurations may apply toother configurations of a storage system that provide other types ofstorage services and/or implementations of the storage services.

FIG. 14 illustrates an example of a data storage system 1400 (“storagesystem 1400”) that includes a file service layer 1402 and a block objectlayer 1404 communicatively coupled to one another with any suitablecommunication technologies. Storage system 1400 may be an exampleimplementation of storage system 1200.

File service layer 1402 may be configured to perform one or moreoperations to provide a file storage service of storage system 1400. Tothis end, file service layer 1402 may manage file service layer entities1406, which may include directories and files arranged in a hierarchicalconfiguration such as a directory hierarchy of a file system.

The file system may be a tree of directories with files as leaf nodes.The directories may provide names for files, some additional filemetadata (often including the file type), and identities for the filesthat are usually distinct from the names that can be used to locate themetadata for storing the content and other metadata for the filesthemselves. For example, many traditional Unix file systems use ani-node number, but other implementations may use other forms of uniqueidentifiers. Directories themselves can also have identifiers, similaror the same as for files, and can be named within their parentdirectories in a similar or identical fashion. These identities ensurethat a file or directory is uniquely identified so that even if it isrenamed, moved, or linked so that it has more than one name, it canstill be referenced. Movement of a file or directory between a sourcedirectory and a target directory may be essentially an operation on thesource and target directories that removes a name at one location forthe moved file or directory and adds a name to another location for themoved file or directory. Linking, likewise, adds an additional name fora file to a target directory.

Block object layer 1404 may be configured to perform one or moreoperations to implement file service layer entities 1406 of the filestorage service of storage system 1400. For example, block object layer1406 may manage block objects 1408 associated with (e.g., that implementor otherwise represent) file service layer entities 1404. The blockobjects 1408 may be configured in any of the ways described herein andmay be operated on by block object layer 1406 to implement file servicelayer entities 1406 and/or other aspects of the file storage system atthe block object layer 1406. The block objects 1408 may beimplementations of a storage system based on concepts in block-basedstorage systems but oriented toward high object counts and dynamiccreation and deletion that are atypical of volume-based block storageand are suitable for storing data and metadata for individual files anddirectories with efficient random read-write access (at least at thelevel of blocks). This may separate out the implementation of a fileservice from the implementation of aspects of a storage system forstoring data and metadata for individual files and directories inresponse to modification requests. As described herein, the blockobjects 1408 provide efficient mechanisms for certain data operations,including cloning and/or data versioning using efficient virtual blockobject snapshots. Block objects 1408 may be stored and managed in ablock object store of block object layer 1404.

In certain examples, block objects 1408 stored in a block object storemay be configured to have an externally visible organization analogousto what is commonly found in object stores, where a key in a simplenamespace identifies an object that stores data. Block objects 1408 maybe configured to support low latency random updates, at least at thelevel of writing and overwriting random blocks. Block objects 1408 maybe configured to have a rich set of primitives for modifying the blockobjects 1408 (richer than primitives of conventional object stores).

In certain examples, block object layer 1404 may be configured tosupport snapshots of block objects 1408, linkage to path sets (whichcould instead be handled by file service layer 1402 or a layerintermediate between file service layer 1402 and block object layer1404), and/or at least block-level random modifications and increases inblock object size such as by writing beyond the current end of a blockobject 1408. Block object layer 1404 may be configured to provideadditional features in other examples.

In certain examples, block objects 1408 may correspond to blockcontainers such as block containers 405 described herein. For example,block objects 1408 may include block containers or be an implementationof block containers.

In addition to supporting reading and writing (and other types ofmodifications) of individual block objects 1408, block object layer 1404may be configured to perform and/or support operations applied to groupsof file service layer entities in file service layer 1402. In order toimplement certain operations applied to groups of file service layerentities 1406 in file service layer 1402, block object layer 1404 mustidentify the block objects 1408 that are associated with the fileservice layer entities 1406 in the groups at the times the operationsare applied in file service layer 1402. For example, for a snapshotoperation applied to a directory of a file system in file service layer1402, block object layer 1404 must identify the block objects 1408associated with the file service layer entities 1406 that are in thedirectory tree of the directory at the time the snapshot operation isapplied to the directory in order to be able to implement a consistentsnapshot of the directory in block object layer 1404. Identifying allthe appropriate block objects 1408 can be time consuming and difficultto implement atomically.

Storage system 1400 may be configured to identify relationships betweengroups of file service layer entities 1406 and block objects 1408associated with the file service layer entities 1406 in advance ofimplementing operations in block object layer 1404. For example, storagesystem 1400 may use an implementation that groups and pairs files,managed directories, and block objects in advance. Storage system 1400may then use those identified relationships to coordinate operations onblock objects 1408, including to implement snapshot operations, cloningoperations, and/or other operations on the block objects 1408. Theserelationships may be represented as path sets 1410.

In certain embodiments, path sets 1410 may be associated with one ormore directories of a file system managed by file service layer 1402 andmay represent collections of block objects 1408 associated with thedirectories (e.g., associated with file service layer entities 1406 ofone or more directory hierarchies of the directories of the filesystem). In certain examples, directory hierarchies to be used foroperations that benefit from path sets 1410 may be designated inadvance, such as by designating directories of the file system as“managed directories” that are designated to support path sets and/orcertain operations such as snapshots, cloning, and/or other operations.File service layer 1402 may be configured to manage directories and thegeneral properties of directories that are designated to be manageddirectories. The set of all files and directories contained within amanaged directory, together with their paired block objects 1408, may berepresented as a path set 1410.

In simple examples, managed directories may start out empty and filesand directories added within them may remain solely within them untildeleted. In such examples, a file or directory cannot move into or outof a managed directory or be linked (e.g., hard linked in Unix parlance)into or out of the managed directory. This may apply generally to anymanaged directories, including managed directories within other manageddirectories, so that, for example, a file created within a secondmanaged directory that is within a first managed directory cannot bemoved or linked out of that second managed directory, and files withinthe first managed directory cannot later be moved or linked into thesecond managed directory.

Such examples may exist when file service layer 1402 is configured toinvoke limitations that prevent movement of files and directories intoand out of managed directories and/or linking of files and directoriesto managed directories. In such examples, files and subdirectories aretypically added to a managed directory when the files or subdirectoriesare created, either as part of creating the managed directory itself orwhen adding files or subdirectories within the managed directory. Filesand subdirectories within a managed directory may be marked as being“live” or “active” with respect to the managed directory. When the filesor subdirectories are removed from the file system namespace, the filesor subdirectories may be marked as no longer being “live” or “active”with respect to the managed directory.

In more complex examples, if a file or directory is added (e.g., moved)within a directory tree of a managed directory, file service layer 1402may mark the file or directory as part of the managed directory. If afile or directory is removed from (e.g., moved out of) of a manageddirectory, file service layer 1402 may mark the file or directory as nolonger part of the managed directory. If a file or directory is linkedfrom one managed directory to another, file service layer 1402 may markthe file or directory as being a member of two managed directories. If adirectory is moved into or out of a managed directory, file servicelayer 1402 may perform a tree walk to recursively mark that directory'sfiles and subdirectories as now being in or no longer being in themanaged directory. Such examples support moving or linking into and outof managed directories.

A file or directory may have some lifetime within a managed directory.When a file or directory is added to a managed directory (such asbecause the file or directory is created), then the file or directory islive within the managed directory. If at some point the file ordirectory is removed from the managed directory (such as because thefile or directory is deleted), then the file or directory is no longerlive within the managed directory. Any operations applied to the manageddirectory during a lifetime of a file or directory in the manageddirectory will apply to the file or directory. For example, anysnapshots of a managed directory between the time a file or directory isadded and the time the file or directory is removed from a manageddirectory will reflect as presented snapshot images of that file ordirectory.

In examples that support files or directories being moved or linked intoor out of a managed directory, storage system 1400 may be configured toallow for multiple lifetime ranges. For example, if a file or directoryis moved out of a managed directory, some snapshots are taken of themanaged directory, and then the file or directory is moved back in tothat same managed directory, then the file or directory has two rangesof snapshots, corresponding to the first time the file or directory wasin the managed directory, and the second time the file or directory wasin the managed directory, and the file or directory is “live” from thesecond time but not from the first time.

In certain examples, a directory may be designated a managed directoryonly at creation of the managed directory or when the directory isempty. In other examples, an existing non-empty directory may bedesignated a managed directory. File service layer 1402 may perform atree walk of a directory designated to be a managed directory and markeach file or subdirectory within the tree as now associated with themanaged directory. Other schemes may be used in other examples to changea non-managed directory to a managed directory.

In certain examples, a managed directory may be created anywhere withina directory tree. In other examples, file service layer 1402 may beconfigured to allow only certain directories to be designated as manageddirectories. For example, managed directories may be limited to certaindirectories such as a root directory, subdirectories within the rootdirectory, and/or a top-level directory of a file system. In otherexamples, path sets 1400 may be established for other configurations ofdirectories and/or all directories of a file system.

In certain examples, storage system 1400 may be configured to allowdirectories within one managed directory to also be designated asmanaged directories, thus causing some files and directories to beassociated with more than one managed directory. Files and directoriesassociated with more than one managed directory may be associated withmore than one set of directory level operations, such as more than oneset of snapshot operations. This may support nested snapshots of nestedmanaged directories.

A managed directory may be any directory that is designated for one ormore management operations, including for establishment of path sets forthe directory and/or for taking snapshots of the directory. Manageddirectories may be configured to support various types of operationsthat may be applied to the managed directories. Such operations may beapplied to a managed directory based on any suitable trigger event. Forexample, file service layer 1402 may apply an operation to a manageddirectory based on a manual trigger such as in direct response to userinput requesting the operation be applied. As another example, fileservice layer 1402 may apply an operation to a managed directory basedon a defined schedule or some other set of defined policies for applyingoperations.

To illustrate, snapshot policies may be associated with a manageddirectory and may include a set of rules for creating snapshots andpossibly a set of rules for retaining the snapshots. The rules forcreating snapshots may specify when snapshots of the managed directoryare taken, and the rules for retaining snapshot may specify how long thesnapshots are retained. For example, a rule of a schedule-based policymay specify that a snapshot be created every hour with snapshots beingretained for twenty-four hours, except that one of every twelve of thosesnapshots (one snapshot from every twelve hours) is retained for fivedays. A trigger-based policy could be related to ransomware detectionmethods, where such detection may trigger creation of a snapshot withlimitations on who and under what circumstances the snapshot can bedeleted. Such ransomware protection snapshots may also guard against thefile system itself being deleted, or at least may guard against adeletion of the file system also deleting ransomware protectionsnapshots. In certain examples, one or more snapshots of a manageddirectory may be read-only, immutable snapshots designed to protectversioned data from being corrupted or destroyed.

File service layer 1402 may be configured to provide access tosnapshots, including access to the content of snapshots and/orinformation about (e.g., a listing of) snapshots. In certain examples,this may be accomplished with a special type of program implementeddirectory that can be accessed to access snapshots. For example, fileservice layer 1402 may provide a program implemented directory called“..snapshots..” that is available within any directory that mightinclude snapshots and that may include policies or other informationrelated to the directory and/or snapshots.

A program implemented directory may be a directory that is accessiblethrough the file system namespace and whose contents are determined byfile service layer 1402 rather than being stored as an explicitlyformatted structure. A program implemented directory may be omitted fromstandard directory content queries to avoid confusing regular directorytraversals (so that, for example, a POSIX or similar “find” commandperforming a directory tree walk would not normally notice the existenceof a “..snapshots..” directory as it would not show up normally wheniterating the entries in a directory. Explicitly opening or traversinginto a “..snapshots..” directory may provide access that can be used tolist snapshots or access policies, but the “..snapshots..” directory maybe otherwise invisible when viewing the file system normally. A similarcapability for accessing snapshots could be added to files as well,either by accessing a file with some special suffix (file..snapshots..)or by accessing the file as if it were a directory (file/..snapshots..).

For example, if there were three snapshots of a managed directory called“managed1,” then the managed1 directory itself, and also possiblysubdirectories of the managed1 directory could each include a (possiblyhidden) program implemented directory “..snapshots..” with, for example,entries of “snapshot.A,” “snapshot.B,” and “snapshot.C.” Descending intoone of these would then access that directory in the context of thatsnapshot. So, “managed1/..snapshots../snapshot.A/subdirectory/file1”would access file1 as it existed within the managed1 directory at thetime of the snapshot. Snapshots associated with policies may include thepolicy name and/or may be organized in some directory structure withinthe “..snapshots..” directory, such as, for example,“..snapshots../policies/<policyname>/snapshot.N.”

Additional information may be provided for richer information aboutsnapshots and policies. For example, a snapshots.info file may providerich information about the snapshots, such as when they were created,how much space they consume, any restrictions on them, etc. Apolicies.info file may provide information about policies, each policy'ssnapshot schedule, or other interesting data. These could be provided inXML format, JSON format, some tabular format, or in any other usefulformat.

Program implemented directories such as “..snapshots..” may be providedwhen traversing a snapshot view (for example, such as through“managed1/..snapshots../snapshot.A/subdirectory/..snapshots..”).Traversing parent directories (such as through“subdirectory/..snapshots../snapshot.B/..”) may be allowed, in whichcase the parent is now in the context of “snapshot.B” instead of“snapshot.A.” As a convenience, if a file or directory is still livewithin a managed directory (it has not been removed from the manageddirectory), then a “snapshot” name such as “live” could be used toaccess the file or directory from a snapshot. So,“managed1/..snapshots../snapshot.A/subdirectory/..snapshots../live/file”may access the live version of a file through a snapshot directory tree.Alternately, a determination may be made as to whether a file is stillconsidered to exist in the live version of a managed directory that isbeing traversed through a snapshot directory tree by, for example,testing whether “file/..snapshots../live” exists.

In certain examples, storage system 1400 may be configured to allow aflexible scheme for identifying snapshots logically or essentiallythrough queries using special names. For example,“..snapshots../snapshot@time=2020-01-02-03:06:00” may reference whateversnapshot was created at or before 03:06 am on Jan. 2, 2020, or“snapshot@time-3h” may reference a snapshot from at last three hoursago.

As mentioned, path sets 1410 may be associated with one or moredirectories of a file system managed by file service layer 1402 and mayrepresent collections of block objects 1408 associated with thosedirectories of the file system. Path sets 1410 may be associated with adirectory such as a managed directory in any suitable way. For example,a managed directory may include or link to metadata that links to a pathset 1410 associated with the managed directory.

In certain examples, a managed directory may be configured to managesnapshots of the managed directory that are taken by file service layer1402, and path sets 1410 associated with the managed directory may beconfigured to manage information representative of the snapshots of themanaged directory and/or implementations of the snapshots in storagesystem layer 1404. The metadata may include policy information thatnames each snapshot and relates snapshots managed by the manageddirectory with snapshots managed by path sets 1410 associated with themanaged directory.

A time order of the snapshots may be defined for snapshots managed bythe managed directory and/or for corresponding snapshots managed by pathsets 1410 associated with the managed directory. For example, path sets1410 may assign each snapshot and/or each corresponding versioned pathset an increasing number so that higher numbers represent more recentsnapshots and/or versioned path sets.

Metadata that associates a managed directory with path sets 1410associated with the managed directory may be implemented in any suitableway. For example, a structure representing the managed directory mayinclude such metadata, a structure representing the path sets 1410 mayinclude such metadata, or any other structure or entity of storagesystem 1400 may include such metadata. The exact details of whatmetadata is held by a structure representing a managed directory andwhat metadata is held by a structure representing a path set 1410, oreven whether these are distinct structures, can vary betweenimplementations. In certain examples, a managed directory may representa presentation of snapshots, and paths sets 1410 associated with themanaged directory may represent an internal relationship that tiestogether block objects 1408 representing files and directories in thedirectory.

In certain examples, how policies relate between managed directories andpath sets 1410 may vary between implementations. For policies whichcause snapshots to be created automatically, for example, path sets 1401may be configured to automatically invoke the snapshots inimplementations in which the path sets 1410 are managed within the blockobject layer 1404 of storage system 1400. The block object layer 1404may, for example, have tighter integration between activity thatmodifies a block object and clocks or other sensors that can be testedwhile performing that activity. That also makes for a convenientdivision of responsibility between presenting a model, which maygenerally happen within the file system service layer 1402 andimplementing that model within the block object layer 1404.

In examples in which snapshots may be generated automatically in theblock object layer 1404 on behalf of path sets 1410, the presentation ofthose snapshots from the file service layer 1202 (the managed directorylayer) may take that into account. For example, the file service layer's1202 presentation of snapshot names may in some cases use a pattern thatcan relate a path set created snapshot to a name presented through amanaged directory-based interface. For example, the path set may knowthe rules for a policy, but a managed directory might define the namefor the policy, so the 100th snapshot created on behalf of a policymight just have the number 100 in the path set structure, but themanaged directory implementation in the file service layer 1402 mayconvert that to “daily/snapshot.100.”

An example version of a relationship between managed directories andpath sets 1410 is to make them the same, or rather to have all thepolicy, naming, and other aspects of a managed directory be held by thepath sets 1410, thus leaving the term “managed directory” to mean aconvenience name for the directory on which a path set is first created.

A path set 1410 may be, basically, a simple collection of files anddirectories. The path set 1410 itself may not necessarily record orunderstand the hierarchical relationships between those files anddirectories. Indeed, because files and directories can be moved aroundand linked within a path set 1410 without altering which path set 1410those files or directories are associated with, such operations can beviewed as leaving the path set 1410 itself unchanged, except to thedegree that the files and directories that are part of the path set aremodified by such operations.

FIG. 15 illustrates example path sets 1500 (e.g., path sets 1500-1 and1500-2) that represent relationships of file service entities 1502 andblock objects (BOs) 1504 that represent the file service entities 1502.As shown, the file service entities 1502 may include directory D1,directory D2, directory D3, and file F1 arranged in a hierarchicalconfiguration such as a directory hierarchy having D1 as the top node,D2 and D3 as children nodes of D1, and F1 as a child node of D2. The BOs1504 may include BO1, BO2, BO3, and BO4 that implement the file serviceentities 1502. Configurations of arrows 1506 (e.g., configurations1506-1 and 1506-2) depict relationships between the file serviceentities 1502 and the BOs 1504 that represent the file service entities1502. As shown by configurations 1506-1 and 1506-2, path set 1500-1 mayrepresent a collection of BOs 1504 (e.g., BO1, BO2, BO3, and BO4) thatare associated with file service entities 1502 in a directory hierarchyhaving D1 as the top node, and path set 1500-2 may represent acollection of BOs 1504 (e.g., BO2 and BO4) that are associated with fileservice entities 1502 in a directory hierarchy having D2 as the topnode.

In the example shown in FIG. 15, each of path sets 1500 is a path setassociated with a different directory of a file system. In certainexamples, path sets 1500 may be established for certain types ofdirectories, such as directories that are designated as manageddirectories, as described above. For example, directories D1 and D2 maybe designated as managed directories to which path identifiers (e.g.,“D1” and “D2”) are assigned and used for path sets 1500. D3 may not be amanaged directory and may not be assigned a path identifier for use inpath sets 1500.

In general, a path set represents less than all configurationinformation about file service entities 1502. For example, a path setmay represent a collection of BOs 1504 that are associated with amanaged directory D1 or D2, without representing information about thehierarchical structures within directory D1 or D2. For example, path set1500-1 may represent that BO1, BO2, BO3, and BO4 are associated withdirectory D1 but may not include any information about the relationshipsbetween BO1, BO2, BO3, and BO4 or the relationships between D1, D2, D3,and D4 within directory D1.

In certain examples, path sets 1410 may be associated with operationsapplied to managed directories D1 or D2 in file service layer 1402. Forexample, file service layer 1402 may apply operations to manageddirectory D1. The application of the operations to managed directory D1may be configured to trigger establishment and/or updating of a path set1410 associated with the managed directory For example, the path set1410 for managed directory D1 may be updated over time to reflectcurrent membership of block objects 1408 in the path set 1410, as blockobjects 1408 are added to and removed from the path set 1410. When aparticular type of group operation is applied to the managed directoryD1, the path set 1410 for the managed directory D1 may be versioned suchas by locking in the membership and content in the path set 1410 as themembership and content existed when the group operation is applied. Thislocked-in membership and content associated with the group operationapplied to the managed directory D1 may be referred to as a version ofthe path set 1410.

In this sense, a path set 1410 may be said to be versioned based onoperations and/or an order in which operations are applied to a manageddirectory. For example, the file service storage layer 1402 may apply afirst particular group operation to the managed directory D1 at a firsttime in a temporal sequence. In response, the storage system 1400 mayrecord a first version of the path set 1410 for the managed directoryD1. The first version of the path set 1410 may indicate the firstoperation, the first time associated with the first operation, and thefiles and directories within the directory hierarchy of the manageddirectory D1 when the first operation is applied to the manageddirectory D1. Subsequently, the file service storage layer 1402 mayapply a second particular group operation to the managed directory D1 ata second time in a temporal sequence. In response, the storage system1400 may record a second version of the path set 1410 for the manageddirectory D1. The second version of the path set 1410 may indicate thesecond operation, the second time associated with the second operation,and the files and directories within the directory hierarchy of themanaged directory D1 when the second operation is applied to the manageddirectory D1.

To illustrate one example, a first snapshot operation is applied to D1shown in FIG. 15, which may in effect mean that the first snapshotoperation is applied to all files and directories (D1, D2, D3, and F1)in the directory hierarchy associated with D1. The storage system 1400may respond by recording a first version of the path set for D1 thatrepresents a collection of block objects BO1, BO2, BO3, and BO4 that arewithin the directory hierarchy of D1 when the first snapshot operationis applied to D1. A change is then made to the directory hierarchy. Forexample, D3 may be removed (e.g., deleted or moved) from the directoryhierarchy. The path set for D1 is updated to reflect that D3 has beenremoved from membership in the path set. A second snapshot operation isthen applied to D1, which may in effect mean that the second snapshotoperation is applied to all files and directories (D1, D2, and F1) inthe directory hierarchy associated with D1. The storage system 1400 mayrespond by recording a second version of the path set for D1 thatrepresents a collection of block objects BO1, BO2, and BO4 that arewithin the directory hierarchy of D1 when the second snapshot operationis applied to D1. In this or a similar manner, versions of the path setfor D1 may be established and may represent collections of block objectswithin the directory hierarchy of D1 when snapshot operations areapplied to D1.

FIG. 16 illustrates an example establishment of versions of a path setfor a directory D1 of a file system. In the illustrated example, a firstversion of a path set 1600-1 for D1 is established in response to afirst snapshot (Snapshot1) being applied to D1. The first version of thepath set 1600-1 represents a collection of block objects (BOs)associated with D1 when the first snapshot is applied to D1.Subsequently, a second version of the path set 1600-2 for D1 isestablished in response to a second snapshot (Snapshot2) being appliedto D1. The second version of the path set 1600-2 represents a collectionof block objects associated with D1 when the second snapshot is appliedto D1. The collection of block objects associated with D1 at the secondsnapshot may be the same as the collection of block objects associatedwith D1 at the first snapshot if no changes to the membership of D1 weremade between the applications of the first and second snapshots to D1.Otherwise, the collections may be different and may reflect anychange(s) made to the membership of D1 between the applications of thefirst and second snapshots to D1. Versions of the path set for D1 maycontinue to be established in association with snapshots being appliedto D1, as is illustrated by an Nth version of the path set 1600-N beingestablished in response to an Nth snapshot (SnapshotN) being applied toD1. The Nth version of the path set 1600-N represents a collection ofblock objects associated with D1 when the Nth snapshot is applied to D1.

Versions of a path set may be indexed in any suitable way, such as byincreasing an index value so that higher index values represent morerecent versions of the path set. The versions of the path set may beused by the storage system 1400 in any suitable way to coordinateoperations on block objects indicated by the path set. For example,creation of a new version of the path set may trigger one or moreoperations of block object layer 1404.

A block object 1408 stores data and some amount of metadata for a fileservice layer entity 1406 such as a file or directory of a file systemmanaged by file service layer 1402. For example, a block object 1408 maystore data and metadata for something stored into the block object 1408by file service layer 1402 that utilizes collections of block objects1408 to store content for the file service layer 1402. For a directory,this data may include a list of directory entries for the files anddirectories to be listed in that directory, identifiers for eachindividual file or directory that can be used by the file service layer1402 to at least find that file or directory's block object, andpossibly a few additional attributes for each entry. For example, acommon item of metadata stored in directories is whether an entryreferences a file or directory. Metadata stored by the block objectlayer 1404 for a directory block object could include additional filesystem information, such as ownership, permissions, and/or variousaccess and modification times. Alternately, much or all of that metadatacould be stored in data blocks within the directory's block object. Incertain examples, “directory” table objects which can store rows orrecords can be used to store structured data representing directories astables, rather than as blocks which the file service layer 1402 storesformatted directory information into. Such an alternate implementationmay require that operations (e.g., snapshot and/or cloning operations)work as described, even if the implementation differs from how data isstored for directories versus how data is stored for files. Such “table”objects may still be referred to as “block” objects for purposes of thepresent application as long as they provide operations (e.g., snapshotand/or cloning operations) and can be modified and read as needed forthe file service layer 1402.

In certain examples, the content of each individual file in a blockobject store may be stored as individual block objects 1408 that eachrepresent the content of that file. The block objects 1408 may haveadditional metadata kept elsewhere or in the block object 1408 (such asin the first one or the first few blocks of a block object 1408).Metadata may include ownership, permissions, time stamps, and/orinformation such as a link count used with linked files that can be usedto determine whether a file is linked from multiple directory entries,such as from multiple directories, and to determine when the last linkto a file has been removed.

Each block object 1408, whether for a file or directory, may have anidentity that can be used to name the block object 1408 that isreferenced by a particular file or directory. This identity might be aname or part of a name. There may be a variety of namespace elements forblock objects 1408, such as a pod, a tenant, a file system, etc. Theidentity stored in a directory for use by a file system to reference ablock object 1408 may be used to generate a full name or unique blockobject identity from other information known by the file system. Thefile system itself could have an identity, for example, and a particularblock object 1408 may be identified by combining the file systemidentity and an identity which is unique within the file system. Theidentity within the file system may, for example, be a simple number asis common in Unix-style i-node based file systems. The file system couldin turn be within a pod or a tenant or some other grouping structure,such as a more traditional object-store style bucket. In a pod-basedsystem, for example, the full identity of a block object 1408 could bedetermined using the pod, the file system, and the block object number.An advantage of such a scheme is that the scheme allows pods or filesystems to be copied by logically copying all of a file system's blockobjects, or all of a pod's block objects, and the file system relativeidentifier stored in the file system's directory entries doesn't have tochange.

For example, if a file system identifier is a 128-bit globally uniqueidentifier, and a pod also has a 128-bit globally unique identifier, andwithin a file system the file system relative identifier for a file ordirectory is a 64-bit number, then the identity of a block object withina pod might be formed from the 128-bit file system identifier and the64-bit file system relative number, but a directory entry might containonly the 64-bit number, which may be stored, for example, as aneight-byte binary value in a binary data structure.

As described above, path sets 1410 may be used to define a set ofsnapshot operations in a time order based on the time order in which thesnapshot operations are applied in the file service layer 1402. Thesnapshot operations may be ordered in any suitable way, such as bynumbering them such that the first snapshot of a path set is number 1,the second is number 2, and so on. Other ordering schemes may be used inother examples.

In certain examples, storage system 1400 may maintain a live version ofeach path set. The live version of a path set represents a datasetcorresponding to the path set that is updated by changes such as writesto a block object, or there may be updates to certain types of metadatathat reflect in the live version but that stay frozen in snapshots justas with the data content of the block object. A number may be assignedto the live version of the dataset, such that this number becomes asnapshot number when the next snapshot is taken. The numbered instancesof the datasets may be called versions, and all but the current andhighest numbered “live” version are effectively snapshots with frozenlogical contents. So, with this, when a path set is first created, thecurrent live version number may be version 1 and there may be no earlierversions. When the first snapshot is taken, the live version advances toversion 2 and version 1 becomes a logically content frozen snapshot.When the second snapshot is taken, the live version advances to version3, making version 2 also a logically content frozen snapshot, and so on.Accordingly, a block object 1408 may include a live version and a set oftrailing, logically content frozen, versions.

A block object 1408 may be associated with some number of path sets.With respect to each associated path set, the block object 1408 may beseen to have a snapshot life span, stretching from a first version heldin the block object 1408 to a last version held in the block object1408. A block object 1408 can be dropped as “live” for a path set, suchas because its file or directory has been removed, resulting in theprevious snapshot being the last version. So, the block object 1408 canbe viewed as having a range of valid path set versions corresponding tothe “live” path set version when the block object 1408 becomes valid inthe path set through to the version where the block object 1408 is nolonger valid in the path set, meaning that the block object 1408 isvalid up until the version before the block object 1408 was removed fromthe path set. If a block object 1408 can be removed from a path set,such as by moving a file or directory out of a path set, and then addedback to the path set, such as by moving that file or directory back tothe path set, then an implementation may support multiple valid ranges.Alternately, a file or directory might be deleted from the live manageddirectory in one version (while that version is live) and restored tothe managed directory in a later version. This can also result inmultiple valid ranges.

A block object 1408, with respect to snapshots and versions, may beviewed as having a “live” writable image and a trailing set of snapshotimages representing prior points in time. If a block object 1408represents a file or directory that has not been removed from the livefile system, then the block object 1408 has a writable image. If theblock object 1408 has snapshots that have not yet been removed, then theblock object 1408 has snapshot images. If the block object 1408 has beenremoved from the file system and all the block object's 1408 reachablesnapshots have been removed, then the block object 1408 can be removedfrom the storage system.

In certain examples in which a block object 1408 knows which path set itis in and in which the block object layer 1404 can understand whichblock objects are in each path set, block object layer 1404 may beconfigured to snapshot each block object 1408 in a path set whenever asnapshot is taken of the path set and associate each such block objectsnapshot with the path set snapshot. For a path set PS1, for example,block object layer 1404 may take a snapshot of each block object 1408 inPS1 each time PS1's version increases and then associate that snapshotwith the now trailing path set version number. So, when PS1 adds a newsnapshot to move from version 3 to version 4, block object layer 1404takes a snapshot of each block object 1408 that is “live” in PS1 andassociate that with PS1 version 3. Version 4 would essentially be thewritable image of the “live” block object 1408. If the block object 1408is also associated with a second path set, PS2, then the block object1408 may have a separately numbered set of versions, and a differentversion number corresponding to its “live” writable image even thoughthe block object 1408 itself only has one writable image which is sharedacross all path sets in which the block object 1408 is live.

But, in a file system with many files and directories, it is common thatmost (in some cases, the vast majority of) files in a file system or ina managed directory are not modified between any two snapshots. Indeed,in many file systems, many if not most files are written once and nevermodified again, though the directories containing those files aremodified to list and reference new files as they are added and to removereference to files as they are deleted. Given that these are commoncases, given that file systems (and managed directories) could storemillions if not billions of files (and thus millions if not billions ofblock objects), and given that there is likely some amount of workneeded to handle snapshots of each block object 1408 in a path set, itmakes sense to optimize the model to avoid doing that work whenever apath set version advances to result in a path set snapshot. This iswhere a valid range for an individual block object within a path set mayapply.

In certain examples, the logical content and tracked logical metadata ofa block object 1408 may remain unchanged until a request from the fileservice layer 1402 requests a change, either by alteringsnapshot-tracked logical metadata or by altering the content of theblock object 1408, such as through a write request or through any othersupported requests for altering block object content or version trackedmetadata. As a result, if the version number of a path set advances,resulting in a path set snapshot, block object layer 1404 may not act onthat for any block object 1408 until a request is received from the fileservice layer 1402 to modify the logical content or version trackedmetadata of the block object 1408. That is, block object layer 1404 maywait for some operation on the block object 1408 itself, such as amodifying operation, before acting on the path set version havingadvanced. Such selective and/or delayed implementation of operations mayconserve and facilitate efficient use of resources of storage system1400.

One way to configure such selective and/or delayed implementation ofoperations is to associate a last modified version (e.g., a last known“live” version) for each block object's association with each of itsassociated path sets. A modification may be a change to the logicalcontent or version tracked metadata for a block object 1408, or aremoval of the block object 1408 from the path set, such as because thefile was deleted from the live file system. Until such a modification orremoval request comes in, no snapshot is taken of the block object 1408.For example, a file F1 in path set PS1 may be created and written andclosed at version 5 of PS1, so that all of F1's current logical contentis at PS1 version 5 and there are no snapshots of F1. The version of PS1may be advanced from 5 to 6 to 7 to 8, resulting in versions 5, 6, and 7being snapshots and version 8 being the live version of PS1. The blockobject 1408 for F1 would still be at version 5 for PS1. Block containerlayer 1404 may receive, from the file service layer 1402, modifyingoperation to the block object 1408 for F1 when the block object's 1408version for PS1 is at version number 5 and PS1's version is at version8. This difference would be detected and would then result in blockobject layer 1404 taking a snapshot of the block object 1408. The liveversion of the block object 1408 would advance to version 8 for PS1. Ifinstead of receiving a request to modify F1, a request is received toremove F1 from PS1, block object layer 1408 may respond by taking asnapshot of the block object 1408 and marking the block object 1408 ashaving been removed at version 8 from PS1.

While the example described in the previous paragraph is directed to afile, the same principles may apply to a directory or other suitableservice layer entity of a data storage service.

The snapshot of the block object 1408 that is taken in response to amodifying or deleting operation that came in after a path set versionadvanced (thus after the snapshot of the path set) may be assigned toall intervening path set version numbers since the last snapshot. Forexample, the snapshot of the block object 1408 may be assigned toversions 5, 6, and 7 in the present example. Alternately, the snapshotof the block object 1408 may be assigned to only one of those versions(for example version 5), which would then imply that versions 6 and 7essentially share the same version as the snapshot for version 5 (as anexample). Storing just one of the numbers may result in storing lessmetadata.

In certain examples, requests to merely examine or retrieve logicalcontent or logical snapshot tracked metadata for a block object 1408,such as requests to read a file or list the content of a directory, maytrigger creating a snapshot and advancing the version of a block object1408 for a path set if the version of the block object 1408 does notmatch a path set's “live” version. In other examples, the currentcontent of the block object 1408 may be examined or retrieved withouttriggering the creation of block object snapshots. In such otherexamples, snapshots of block objects 1408 may be taken just in time,i.e., just before being modified or deleted.

Accessing snapshots of block objects 1408 may be similarly configured.Snapshot access may have a context defined by a combination of a manageddirectory and a path set, which may result in a block object 1408 beingaccessed in the context of a particular path set version number. Theseversion numbers may be created on access if they do not yet exist, orpath set version numbers may be mapped to whatever path set versions theblock object 1408 has acted on as a result of modifying, deleting, orpath set-changing move or link operations. For example, in the exampledescribed above, a request to access snapshot 6 or 7 of PS1 would resultin accessing version 5 of PS1. If version 7 of PS1 is accessed beforemodifications result in a snapshot and the advancement of the blockobject 1408 to PS1 version 8, then the block object 1408 may considerversion 5 of the block object 1408 to be modifiable in that version 5 ofthe block object 1408 will not yet have been converted into a snapshot.

This could result in a race condition, though, if care is not used toavoid such a race condition. The race condition may occur as a result ofaccessing a non-snapshot version of the block object 1408 on thepresumption that the non-snapshot version of the block object 1408 isunchanged while at the same time a modifying operation comes inresulting in the creation of a snapshot and the advancing of the “live”version number associated with the path set to a new number. Themodified data may be inadvertently read if: the retrieval throughsnapshot version 7 first checks that the live version has not advanced;then, the modifying operation makes a snapshot, advances the liveversion, and then modifies the block object; and then, the retrievaloperation through snapshot version 7 reads the live block object on thepresumption that it is still at path set PS1 version 5. This racecondition may be avoided by preventing simultaneous operations or bytaking a snapshot, thus freezing version 5, and advancing the blockobject to 8 before reading from version 5 through snapshot version 7.

Another way to avoid such a race condition is to use an implementationwhere snapshots of block objects 1408 are not so much created as new“live” versions are created, leaving previous versions behind aseffective snapshots. In that model, when a modification happens atversion 8, a snapshot is not created that then becomes version 5, butinstead version 5 is simply left behind as now unchanging and a newversion 8 starts being written that no longer modifies version 5. Then,the snapshot version 7 retrieval of content through version 5 will besafe from race conditions involving creation of a snapshot. Thisapproach may avoid causing a race condition without having to implementsome locks to avoid simultaneous operations and without having to createunnecessary snapshots.

In this approach, if a block object 1408 is associated with two pathsets and one advances and the other does not, then there may beconfusion where for one path set the current “live” version freezes intoa snapshot and for another path set the current “live” version remainsmodifiable. For example, in the above case where PS1 advances fromversion 5 to version 6, and then 7, and then 8, and is then written, foranother path set that the block object 1408 is associated with, say PS2,the path set version has remained at, say, 20, that whole time withoutadvancing. The block object 1408 may freeze at version 5 of PS1 andadvance to a new writable image for version 8 of PS1, but the blockobject 1408 cannot do the same with version 20 for PS2 because thatshould still be writable. This potential issue may be handled, though,by manipulating the relationship between internal versions of the blockobject 1408 and versions associated with path sets. For example, therecould be an internal version of a block object 1408 that advances everytime a snapshot is left behind that results from a modifying operation.The “live” version of any path set would then be updated to track theseadvances in the block object 1408, while snapshots would not. So, ablock object 1408 may be at internal version 100 when the firstmodifying operation is received after PS1 advances to version 8, PS1version 5 for the block object 1408 may be left behind as referencingversion 100, the block object 1408 itself may then advance to internalblock object version 101, PS1 version 8 for the block object 1408 mayadvance to internal block object version 101, and PS2 version 20 wouldbe modified to advance to internal block object version 101 as well.

In this approach, reads of a block object 1408 through a version, sayversion N, of a path set (either the live version or a snapshot version)may either read from the internal version of the block object 1408 thatis associated with path set version N for the block object 1408, or mayread from the most recent path set version known to the block object1408 that is prior to version N.

As described previously, in some implementations block objects 1408 canbe removed from and then added back to path sets and may have ranges ofvalidity from when first added to a path set (such as when thecorresponding file or directory is created) to when removed from a pathset (such as when the file or directory is deleted). This can result inranges of validity of path set versions for a particular block object1408, including multiple ranges in some implementations. When traversingthrough a snapshot directory tree from a snapshot of a manageddirectory, the validity ranges do not present a problem. Any particularfile or directory either exists in that snapshot or does not exist inthat snapshot, and if a particular file or directory was not in thedirectory tree when that snapshot was taken, then the file or directorywill not exist during that traversal either. But this may complicate thepresentation of snapshots when viewing what snapshots of a file ordirectory are available from other files and directories, such asthrough a “..snapshots..” namespace on a subdirectory or file describedearlier as an example snapshot presentation model. Only valid snapshotsshould be listed in such cases, otherwise there could be referentialintegrity issues such as from entering a version of a directory thatshouldn't exist in the managed directory and then accessing the parentdirectory in that context, which might not exist at all because it wasfirst created after that snapshot.

As long as a block object's 1408 most recent valid range for a path setis marked as now invalid when the block object 1408 is removed from apath set, and a new range for a path set is established when a blockobject 1408 is added to a path set, including when adding back to a pathset that it had been in previously, the valid snapshots relative to anypath set can be deduced. To continue the previously described example,if instead of being modified in PS1 version 8, the file represented bythe block object 1408 had been moved out of the path set, then the blockobject 1408 would be updated to indicate that the block object 1408 wasvalid for PS1 from starting at version 5 and was invalid for PS1starting at version 8. If some set of new snapshots are taken of PS1,advancing it to version 12, then if the file is added back to PS1, thena new valid range will be established starting at version 12. Note thatif the file still has not been modified, then the content for version 12is still in the internal version associated with version 5, though itmay make sense to reference that internal version from a version 12rather than relying on uses of version 12 to realize the content reallycomes from version 5 (though that would also work). The validity rangesmay provide a way of listing and accessing only those snapshots of apath set that should be valid for a particular file or directory. So, inthis example, a program that determines the content of the“..snapshots..” program implemented directory for a file or directorythat is not valid from version 8 through version 11 may see from theblock object's 1408 valid ranges for the path set that versions 8through version 11 are not valid and can then avoid listing thecorresponding managed directory snapshots.

Block containers 1408 can be inexpensively versioned in animplementation that supports very low overhead snapshots. However,relating together all the files and directories within a particulardirectory can be an expensive operation at least because doing so mayentail reading all the directories in a tree walk that could involvereading and analyzing entries in thousands or millions of directoriesand linking to thousands to billions of block objects 1408 representingeach individual file.

But certain cases are inexpensive. One example is taking snapshots ofindividual files. Taking a snapshot of an individual file involvessnapshotting one block object 1408, tracking that a snapshot took place,and providing a way to view the snapshot. To handle this, block objects1408 could list, and provide names or numbers for, snapshots that arenot related to path sets. A variant approach is to give a block object1408 a private path set that works the same as regular path sets butthat is local to that individual block object 1408. This private pathset could be provided even for block objects that represent files ratherthan directories. These snapshots might be presented only through thatfile or directory's individual snapshot presentation model (such asthrough the file's “..snapshots..” program implemented directory). Or,there may be some way of listing and accessing from the vantage point ofa directory the available versions of all that directory's containedfiles and directories separately or in addition to listing and accessingversions from the containing directory itself.

One aspect that may be accounted for at the interface between the fileservice layer 1402 and the block object layer 1404 is that the fileservice layer 1402 may need to understand whether it is accessing thelive version of a block object or a snapshot version of a block object,and it may be configured to do so with client protocols that keep fileaccess context in client-held identifiers. And, if Posix-style (Unix,Linux) client access is desired, a live version of a file versus eachsnapshot of a file may have a different reported 64-bit i-node numberwithin each exported file system.

Ignoring the i-node issue, identifiers can simply include snapshotinformation from the path set, such as an identifier for the path setitself, and the number or other identifier of a snapshot of the pathset. These identifiers can be reported for directory listings within aparticular snapshot, for example, and then can be supplied back to thefile service layer 1402 from a client interested in accessing aparticular file or directory within that directory.

Handling the i-node number issue can be more complicated. Posixgenerally expects i-node numbers to be unique within a presented filesystem, and snapshots of files and directories are essentiallyadditional unique files from that perspective. As a result, allsnapshots of all files and directories may have unique i-node numberswithin a file system, so storage system 1400 may be configured to avoidclashes of these i-node numbers. One solution is to make snapshots offiles into distinct file systems from the standpoint that each snapshothas a distinct file system identifier. This could work in some cases,but some distributed file system protocols and client implementations(such as NFS v3) may support this poorly. An alternative is to carve outranges of numbers from the 64-bit i-node number space to be used forindividual path set snapshots. For example, 36 bits of each 64-biti-node number may be associated with a particular file or directory, and28 bits of each 64-bit i-node number may then be associated with aparticular path set snapshot (forming a snapshot number space embeddedwithin the i-node number). This would allow for 64 billion files anddirectories, and 256 million path set snapshots in some implementations.Note that every snapshot of every path set may require a distinctnumber, though numbers could be reused from deleted snapshots.

In such a scheme, live files and directories may be associated withparticular i-node snapshot number space, for example, 0. There could bea simple mapping from the live i-node snapshot number space to aparticular path set snapshot's snapshot number space. For example, ani-node number in the live i-node snapshot space might map to a snapshotby using the number within the live i-node snapshot space and using thatnumber within the path set snapshot's snapshot number space. So, if weuse the notation snapshot-space.i-node-number as a nomenclature for ani-node number within a snapshot number space, then if snapshot numberspace 0 means the live file system and snapshot 5 of path set PS1 has asnapshot number space of 27, then a file with live i-node 300 might be0.300 for the live version of the file and 27.300 for the version of thefile in path set PS1 snapshot 27. Note that if a file or directory isdeleted from the live file system, it may no longer be present in thelive i-node snapshot number space, but the file may still exist insnapshots. As a result, storage system 1400 may be configured to ensurethat a live i-node number is not reused until all snapshots of thecorresponding block object have been deleted.

Other mapping schemes are reasonably possible, depending on the filesystem implementation, file system network access protocols, and filesystem network client implementations. Generally, a mapping schemeshould map file and directory identifiers to identifiers for files in aparticular path set snapshot. In certain examples, the mapping schemeshould be straightforward to determine which block object corresponds toa particular file service layer identifier. In the i-node number schemeprovided above, for example, the i-node number 27.300 corresponds to theblock object with number 0.300, even if the file for that block objecthas been deleted from the file system.

Note that the result of reading a directory differs between reading alive directory and reading a snapshot of a directory, at least becausethe identifiers of referenced files and directories stored in thedirectory's block object may identify the live files and directories. Asa result, the file service layer 1402 may be configured to interpretthose identifiers and convert them into identifiers appropriate for thesnapshot. So for example, in the case described in the previous twoparagraphs, a directory might store an i-node number 0.300 for theparticular file described, but when reading the directory in the contextof the snapshot whose i-node snapshot number space is 27, the filesystem service layer may convert to that to 27.300. If directories storedifferent kinds of identifiers than such i-node numbers, then anappropriate different transformation may be used instead.

FIG. 17 illustrates an example of a storage system establishing andusing versions of a path set to coordinate implementation of snapshotoperations. In FIG. 17, a time axis 1702 depicts a time order in whichoperations are performed. The time axis 1702 may represent time orderusing any suitable units, such as counter values and/or time values. Theoperations may be performed by a storage system or any component(s)thereof, including any of the example storage systems and componentsdescribed herein.

As shown, at a time value of 10 (t=10), a first snapshot, “Snapshot1,”is taken of directory D1. In response, a version of a path set 1704-1for D1 is established. The version of the path set 1704-1 may includeinformation indicating its association with Snapshot1 and a collectionof files and directories that are in the directory tree of D1 at thetime Snapshot1 is applied to D1, as is represented by the first versionof the path set 1704-1 positioned in line with time t=10. Those filesand directories may include a file that is implemented by a block object1706-1. At the time Snapshot1 is applied to D1, block object 1706-1 mayinclude a live version of itself and no snapshot versions, as isrepresented by BO Live 1706-1 positioned at time t=10.

At a time value of 20 (t=20), a second snapshot, “Snapshot2,” is takenof directory D1. In response, a second version of the path set 1704-2for D1 is established. The second version of the path set 1704-2 mayinclude information indicating its association with Snapshot2 and acollection of files and directories that are in the directory tree of D1at the time Snapshot2 is applied to D1, as is represented by the secondversion of the path set 1704-2 positioned in line with time t=20. Thosefiles and directories may still include the file that is implemented byblock object 1706-1. At the time Snapshot2 is applied to D1, blockobject 1706-1 may still include a live version of itself and no snapshotversions, as is represented by BO Live 1706-1 positioned at time t=20.

At a time value of 25 (t=25), a request 1708 to modify block object1706-1 is received. The requested modification may include any requestedchange to the data or metadata of the block object 1706-1, including arequest to delete the block object 1706-1 or its data or metadata, or arequest to write to the data or metadata of the block object 1706-1. Inresponse to the request 1708, a storage system may determine whether totake one or more snapshots of the block object 1706-1 before performingthe requested modification. The determination may be made based on theversions of the path set of D1 and on any snapshot versions of the blockobject 1706-1. For example, the storage system may determine that blockobject 1706-1 has no snapshot versions related to D1, that the firstversion of the path set 1704-1 indicates a first pending snapshot of D1when block object 1706-1 is included in D1, and that the second versionof the path set 1704-2 indicates a second pending snapshot of D1 whenthe block object 1706-1 is included in D1.

Based on these determinations, the storage system may create 1710 one ormore snapshots of the block object 1706-1 in order to implement thefirst and second pending snapshots of D1 before modifying the blockobject 1706-1. This may include creating snapshot versions of the blockobject 1706-1. For example, the storage system may create a firstsnapshot version 1712-1 that corresponds to Snapshot1 of D1 and a secondsnapshot version 1712-2 that corresponds to Snapshot2 of D1. After thesesnapshots are created, the block object may include a live version1706-1 and snapshot versions 1712-1 and 1712-2. Alternatively, thestorage system may create a single snapshot version of the block objectthat corresponds to both pending snapshots of D1 (because the data ofthe block object did not change between the pending snapshots, onesnapshot can be used for both pending snapshots).

After creating the snapshots of the block object, the storage system mayapply 1714 the requested modification to the block object by applying itto the live version of the block object. After the modification isapplied, the block object may include a modified live version 1706-2 andsnapshot versions 1712-1 and 1712-2 (or just one snapshot version in analternative implementation).

Another approach to establishing and using path sets to coordinateimplementation of operations such as snapshots will now be described inrelation to storage system 1400. FIG. 18 illustrates a directoryhierarchy 1802 that includes directory D1, directory D2, directory D3,and file F1 arranged in a hierarchical configuration having D1 as thetop node, D2 and D3 as children nodes of D1, and F1 as a child node ofD2. D1, D2, D3, and F1 may be managed by file service layer 1402. D1,D2, D3, and F1 may be implemented by block objects (BOs) 1804 thatinclude BO1, BO2, BO3, and BO4, which may be managed by block objectlayer 1404.

Storage system 1400 may establish path sets 1810 for the BOs 1804. Thepath sets may be entity-level path sets in that each of the BOs 1804 mayhave a corresponding path set established and associated with that BO1804. A path set may indicate any managed directories associated with aBO. For example, D1 and D2 may be designated as managed directories foruse with path sets and/or certain operations (e.g., snapshots). D1 andD2 may be assigned path identifiers (e.g., “D1” and “D2”) for use in thepath sets.

In the example shown in FIG. 18, a path set for BO1 indicates that BO1is associated with a file storage element in a directory tree of D1. Inthis case, BO1 represents D1, which is part of its own directory tree. Apath set for BO2 indicates that BO2 is associated with a data storageelement in directory trees of D1 and D2. In this case, BO2 representsD2, which is part of its own directory tree and the directory tree ofD1. A path set for BO3 indicates that BO3 is associated with a datastorage element in directory trees of D1 and D2. In this case, BO3represents F1, which is part of the directory tree of D1 and thedirectory tree of D2. A path set for BO4 indicates that BO4 isassociated with a data storage element in the directory tree of D1. Inthis case, BO4 represents D3, which is part of the directory tree of D1.D3 and D4 may not be considered to be part of their own directory treesfor one or more reasons, such as D3 being a file rather than a directoryand D4 being a directory that is not designated a managed directory.

Storage system 1400 may be configured to establish and maintainentity-level path sets such as path sets 1810 in any suitable way. Forexample, storage system 1400 may establish path sets for block objects1804 that implement files and directories of a directory hierarchy 1802of a file system when the files and directories are created and mayupdate the path sets 1810 when configurations of the files anddirectories implemented by the block objects 1804 change (whichconfiguration changes in the file service layer 1402 may cause blockobject layer 1404 to update metadata for the block objects 1804).Storage system 1400 may be configured to use such path sets 1810 tocoordinate implementation of operations on the block objects 1804. Forexample, snapshots applied to D1 and/or D2 by file service layer 1402may be selectively implemented on block objects 1804 based on path sets1810.

FIG. 19 illustrates an example of a storage system using a path set 1810to coordinate implementation of snapshot operations on a block object1804. In FIG. 19, a time axis 1902 depicts a time order in whichoperations are performed. The time axis 1902 may represent time orderusing any suitable units, such as counter values and/or time values. Theoperations may be performed by 1400 storage system or any component(s)thereof, or by any other appropriately configured storage system ofcomponent(s) thereof.

As shown, at a time value of 10 (t=10), a first snapshot, “Snapshot1,”is taken of directory D1. In response, the first snapshot operationapplied to D1 is logged 1904-1. The logging of the operation may includereceiving and storing any information about the operation, such as atime the operation is applied to D1 and an association of the operationto D1. At the time Snapshot1 is applied to D1 and/or logged, a blockobject (BO3) that represents file F1 in directory hierarchy 1802 mayinclude only a live version of BO3, as is represented by BO3 Live 1906-1positioned at time t=10. A path set 1908-1 is associated with BO3, suchas by being associated with BO3 Live 1906-1 as shown in FIG. 19.

At a time value of 20 (t=20), a second snapshot, “Snapshot2,” is takenof directory D1. In response, the second snapshot operation applied toD1 is logged 1904-2. The logging of the operation may include receivingand storing any information about the operation, such as a time theoperation is applied to D1 and an association of the operation to D1. Atthe time Snapshot2 is applied to D1 and/or logged, BO3 includes only alive version of BO3, as is represented by BO3 Live 1906-1 positioned attime t=20. The path set 1908-1 associated with BO3 remains unchanged attime t=20.

At a time value of 25 (t=25), a request 1910 to modify BO3 is received.The requested modification may include any requested change to the dataor metadata of BO3, including a request to delete BO3 or its data ormetadata, or a request to write to the data or metadata of BO3. Inresponse to the request, storage system 1400 may determine whether totake one or more snapshots of BO3 before performing the requestedmodification. The determination may be made based on the path set 1908-1associated with BO3, any snapshot versions of BO3, and logs of snapshotsapplied in file service layer 1402. For example, storage system 1400 maydetermine that BO3 has no snapshot versions related to D1, that path set1908-1 indicates the BO3 is associated with D1 and D2, and that pendingsnapshots of D1, Snapshot1 and Snapshot2 have been applied to D1. Thedetermination may be made in any suitable way, such as by storage system1400 identifying D1 and D2 in the path set 1908-1 associated with BO3,querying logged snapshots to identify any pending snapshots of D1 andD2, and for any identified pending snapshots of D1 and D2 determiningwhether any matching snapshot versions of BO3 have already been taken orhave yet to be taken. In this example, storage system 1400 may identifypending snapshots Snapshot1 and Snapshot2 as being associated with D1indicated in path set 1908-1 and that corresponding snapshots of BO3have yet to be taken for Snapshot1 and Snapshot2.

Based on these determinations, storage system 1400 may create 1912 oneor more snapshots of BO3 in order to implement the first and secondpending snapshots of D1 in the block object layer 1404 before modifyingBO3. This may include creating snapshot versions of BO3 Live 1906-1. Forexample, storage system 1400 may create a first snapshot version 1914-1that corresponds to Snapshot1 of D1 and a second snapshot version 1914-2that corresponds to Snapshot2 of D1. After these snapshots are created,BO3 may include a live version 1906-1 and snapshot versions 1912-1 and1912-2. Alternatively, storage system 1400 may create a single snapshotversion of BO3 that corresponds to both pending snapshots of D1 (becausethe data of BO3 did not change between the pending snapshots, onesnapshot can be used for both pending snapshots).

After creating the snapshots of BO3, storage system 1400 may apply 1916the requested modification to BO3 by applying it to BO3 Live 1906-1.After the modification is applied, BO3 may include a modified liveversion 1906-2 and snapshot versions 1914-1 and 1914-2 (or just onesnapshot version in an alternative implementation). If the modificationdoes not remove BO3 from D1 or D2 (or another managed directory), pathset 1908-1 of BO3 may remain unchanged. If the modification removes BO3from D1 or D2 (or another managed directory), storage system 1400 maymodify path set 1908-1 to reflect the change.

FIGS. 20-22 depict illustrative methods. While FIGS. 20-22 illustrateexample operations according to certain embodiments, other embodimentsmay omit, add to, reorder, and/or modify any of the operations shown inFIGS. 20-22. Operations of any of the illustrative methods may becombined with operations of any of the other methods in any suitableway. One or more of the operations shown in FIGS. 20-22 may be performedby a storage system, any components included therein, and/or anyimplementation thereof.

FIG. 20 depicts an illustrative method 2000. In operation 2002, astorage system establishes path sets. The storage system may establish(e.g., create and maintain) the path sets in any suitable way, includingin any of the ways described herein. The path sets may be configured inany of the ways described herein or in another suitable way.

In operation 2004, the storage system coordinates implementation ofoperations based on the path sets. Operation 2004 may be performed inany suitable way, including in any of the ways described herein. Forexample, the storage system may use the path sets to coordinateselective and/or delayed implementation, in a storage layer of thestorage system, of operations that have been applied to a service layerof the storage system.

FIG. 21 depicts an illustrative method 2100. In operation 2102, astorage system establishes path sets. The storage system may establish(e.g., create and maintain) the path sets in any suitable way, includingin any of the ways described herein. The path sets may be configured inany of the ways described herein or in another suitable way.

In operation 2104, the storage system establishes that an operationapplied to a directory hierarchy of a file system at a first time is tobe selectively implemented later in time. Operation 2104 may beperformed in any suitable way, including in any of the ways describedherein. For example, the storage system may detect and/or log anapplication of an operation (e.g., a snapshot operation) to thedirectory hierarchy in a service layer of the storage system.

In operation 2106, the storage system detects a request to modify astorage layer entity (e.g., a block object) at a second time. Operation2106 may be performed in any suitable way, including in any of the waysdescribed herein. For example, a storage layer of the storage system mayreceive a request to modify the storage layer entity.

In operation 2108, the storage system implements the operation on thestorage layer entity based on a path set. Operation 2108 may beperformed in any suitable way, including in any of the ways describedherein. For example, the storage system may determine, based on the pathset, that the operation applies to the storage layer entity and has notyet been implemented on the storage layer entity. Based on thisdetermination from the path set, the storage system may then implementthe operation on the storage layer entity in response to detecting therequest to modify the storage layer entity.

In operation 2110, the storage system modifies the storage layer entity.Operation 2104 may be performed in any suitable way, including in any ofthe ways described herein. For example, the storage system may modifythe storage layer entity in response to the request detected inoperation 2106 only after the storage system has implemented theoperation on the storage layer entity in operation 2108 (in cases wherethe storage system determines the operation is to be implemented on thestorage layer entity).

FIG. 22 depicts an illustrative method 2200. In operation 2202, astorage system receives a request to modify a storage layer entity(e.g., a block object). Operation 2202 may be performed in any suitableway, including in any of the ways described herein. For example, astorage layer of the storage system may receive the request to modifythe storage layer entity from a service layer of the storage system.

In operation 2204, the storage system determines, based on a path setindicating a relationship between the storage layer entity and adirectory of a file system, that there is a pending operation on thedirectory that is yet to be applied to the storage layer entity.Operation 2204 may be performed in any suitable way, including in any ofthe ways described herein.

In operation 2206, the storage system applies the pending operation tothe storage layer entity. Operation 2206 may be performed in anysuitable way, including in any of the ways described herein. Operation2206 may be performed in response to the determination in operation 2204and before the request to modify the storage layer entity is implementedon the storage layer entity.

In operation 2208, the storage system modifies the storage layer entity.Operation 2208 may be performed in any suitable way, including in any ofthe ways described herein. Operation 2206 may be performed in responseto the determination in operation 2204 and after the pending operationis applied to the storage layer entity.

Path sets may be established and used in any of the ways describedherein and/or in other suitable ways. As an example, path sets may beused for physical space accounting operations, such as to determine howmuch space may be reclaimed when a directory is deleted from a filesystem. As another example, path sets may be used to support nestedsnapshots of nested directories of a file system. For instance,snapshots may be taken of each managed directory in a file system,including of a root directory (which may be a managed directory bydefault) and any subdirectories that are managed directories. In certainexamples, snapshots and path sets may be applied to any directoriesinstead of being limited to managed directories or certain directories.

An interesting issue can come up with space accounting in storagesystems that are capable of accounting for deduplication, clones, andother forms of physical block sharing between block file systems andblock objects. Specifically, when considering physically stored blocks(and possibly the space that they consume after compression or otherdata reduction techniques, and possibly including the additionalcapacity such as that required to make the stored blocks recoverablefrom faults) reporting for blocks that could be shared between multiplelogical addresses within the same or different logical storage entities(files, objects, block objects, volumes, managed directories, filesystems, pods, etc.) a distinction can be made between physically storedblocks that are shared beyond the logical storage entity and physicallystored blocks that are not shared beyond the logical storage entity. Forexample, a volume may include some number of blocks that are unique tothat volume (there may be multiple references within the volume, but thephysical blocks are not shared with other storage entities managedwithin the storage system) and some number that are not unique to thatvolume (the physical blocks are shared with at least one other storageentity managed within the storage system, which could be another volumeor could be some other kind of entity including a file, object, or blockobject). Reporting of shared blocks may be broken down further toaccount for the fraction of references from the particular logicalentity, such as the volume in this example. For example, there could bea first volume and a second volume where the first volume has ten uniqueblocks, the second volume has five unique blocks, and the first volumeincludes two references to a particular shared block, and the secondvolume includes three references to the particular shared block. In thisexample, the first volume has ten unique blocks and one shared block,and the second volume has five unique blocks and one shared block.Further, the first volume might be considered to include 40% of thereferences to the shared block and the second volume might be consideredto include 60% of the references to the shared block. There are manyother ways that this accounting might occur, but there is at least afundamental distinction between unique blocks for a logical storageentity and shared blocks between logical storage entities.

Specifically in the context of managed directories and path sets, spaceaccounting may be provided on a managed directory basis to describeunique versus shared space consumed by all files that are part of amanaged directory, such that unique and shared physical spaceconsumption is reported in some useful way, possibly extended to someuseful description of space consumed by snapshots of files and manageddirectories.

In a block object-based storage system with path sets linking togetherblock objects associated with a particular managed directory, thestorage system may provide accounting for unique versus shared blocks asdescribed above for managed directories. This can be done by having thestorage system perform the logical calculations based on logicalreferences to stored blocks as described above but then doing so foreach path set associated with each block object. By accumulating foreach path set the accounting of unique versus shared blocks and,depending on the implementation, possibly further accounting for theirassociated physical capacity from various combinations of data reductionand overhead for fault recovery, managed directories can be providedwith this kind of granular information on actual space consumption. Thisis particularly interesting and/or useful for multi-level manageddirectories where shared blocks at a lower layer in a hierarchy ofmanaged directories might well be unique blocks at a higher layer, asone managed directory that is a subdirectory within a higher manageddirectory might share duplicate blocks, such as through a deduplicationprocess or through block or block object virtual copy or cloneoperations, with block objects in another managed directory that is asubdirectory within the same higher managed directory.

An example where these kinds of multi-directory-level calculations canbecome particularly interesting and/or useful is when a lower-levelmanaged directory is entirely cloned to another lower-layer manageddirectory beneath the same higher-level managed directory. In this case,all of the blocks in both lower-level managed directories become sharedblocks, possibly with fractional assignment of capacity to each of thetwo managed directories, yet the higher-level directory's counts ofshared and unique blocks would remain largely unchanged. As blocks arewritten to block objects in each of those two lower-level manageddirectories or as new files are added or deleted, or as othermodifications result in changes to shared and unique blocks andcalculated capacities, the two lower-layer directories will diverge fromeach other while the higher-layer directory may continue to accumulatecounts of unique blocks, shared blocks, and calculated capacities basedon the combination of the higher-layer managed directory's combinedblock objects.

U.S. provisional patent application 63/077,259, filed Sep. 10, 2020 andwhich is already incorporated herein by reference, describes examples ofspace accounting. Those examples may be implemented and/or otherwisecombined with path sets in any way suitable for space accounting. As anexample of a way of referencing shared versus unique blocks, and forcloning ranges of logical blocks or other logical storage elements, seeU.S. patent application Ser. No. 15/842,850 filed Dec. 14, 2017, thecontents of which are hereby incorporated by reference. In particular,the '850 patent application describes an illustrative model of leaf andcomposite logical extents and a model for referencing shared blocks bycontent identifier from those extents. The model is suitable forcloning, snapshots, and inline and post process deduplication.

Calculations of unique and shared blocks, and possibly the partialattribution of stored capacity based on the pattern of block shareswithin and between path sets (and thus within and between manageddirectories) can be useful for various purposes. This can be provided tousers to give them an understanding of space consumption that takesshared and unique space into account. This can be used as part of acharge-back model where clones and deduplication can reduce the amountscharged back, or where fractional attribution of shared blocks can beincluded in charge-back calculations. These can also be used as part ofa quota model, whereby operations that would increase unique andfractionally attributed capacity can be prevented or can yield a warningof some kind. In such a case, a quota may apply at a higher-layerdirectory, allowing any amount of cloning, virtual copying, or duplicatecontent within and across the various objects and lower-layerdirectories (including lower-layer managed directories) within thathigher-layer directory without that cloned, copied, or duplicate contentadding significantly or at all against the quota. Metadata overhead maystill add some amount to such a quota.

In the preceding description, various exemplary embodiments have beendescribed with reference to the accompanying drawings. It will, however,be evident that various modifications and changes may be made thereto,and additional embodiments may be implemented, without departing fromthe scope of the invention as set forth in the claims that follow. Forexample, certain features of one embodiment described herein may becombined with or substituted for features of another embodimentdescribed herein. The description and drawings are accordingly to beregarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A data storage system comprising: a memorystoring instructions; and a processor communicatively coupled to thememory and configured to execute the instructions to: establish a pathset that represents a collection of storage layer entities associatedwith service layer entities of a directory hierarchy of a file system;and coordinate, based on the path set and on operations applied to oneor more of the service layer entities of the directory hierarchy of thefile system, implementation of the operations on the storage layerentities.
 2. The data storage system of claim 1, wherein: the servicelayer entities comprise files and directories within the directoryhierarchy of the file system; and the storage layer entities compriseblock objects implementing the storing of content of the files anddirectories.
 3. The data storage system of claim 1, wherein: theoperations comprise a snapshot of a directory associated with thedirectory hierarchy of the file system; and the coordinatingimplementation of the operations on the storage layer entities comprisesimplementing the snapshot on a storage layer entity of the storage layerentities in response to a request to modify the storage layer entity. 4.The data storage system of claim 3, wherein: the snapshot is applied tothe directory at a first time; and the implementation of the snapshot onthe storage layer entity is delayed until a modification of the storagelayer entity is requested at a second time subsequent to the first time.5. The data storage system of claim 3, wherein the request to modify thestorage layer entity comprises a request to delete the storage layerentity or a request to write to the data or the metadata of the storagelayer entity.
 6. The data storage system of claim 3, wherein: theoperations further comprise a snapshot of a subdirectory of thedirectory associated with the directory hierarchy of the file system;and the coordinating implementation of the operations on the storagelayer entities comprises implementing the snapshot of the subdirectoryon the storage layer entity in response to the request to modify thestorage layer entity.
 7. The data storage system of claim 1, wherein:the path set is a first version of the path set; the processor isconfigured to execute the instructions to establish an additionalversion of the path set that represents an additional collection ofstorage layer entities associated with service layer entities of thedirectory hierarchy of the file system; the first version of the pathset corresponds to a first operation of the operations, the firstoperation applied, at a first time, to the directory hierarchy of thefile system; and the additional version of the path set corresponds to asecond operation of the operations, the second operation applied, at asecond time subsequent to the first time, to the directory hierarchy ofthe file system.
 8. The data storage system of claim 7, wherein: thefirst version of the path set represents the collection of storage layerentities that are associated with service layer entities of thedirectory hierarchy of the file system at the first time; and theadditional version of the path set represents the additional collectionof storage layer entities that are associated with service layerentities of the directory hierarchy of the file system at the secondtime.
 9. The data storage system of claim 8, wherein the additionalcollection of storage layer entities that are associated with servicelayer entities of the directory hierarchy of the file system at thesecond time is different from the collection of storage layer entitiesthat are associated with service layer entities of the directoryhierarchy of the file system at the first time.
 10. The data storagesystem of claim 1, wherein: the directory hierarchy of the file systemis associated with a managed directory designated to be managed withpath sets.
 11. The data storage system of claim 1, wherein: the servicelayer entities are managed by a service layer of the data storagesystem, the service layer configured to provide a data storage service;the storage layer entities are managed by a storage layer of the datastorage system; and certain aspects of the data storage service areseparated from the service layer for implementation by the storagelayer.
 12. The data storage system of claim 11, wherein: the servicelayer maintains configuration information representing the directoryhierarchy of the file system; and the storage layer entities of thestorage layer do not maintain configuration information representing thedirectory hierarchy of the file system.
 13. The data storage system ofclaim 1, wherein the operations comprise at least one of a snapshotoperation, a cloning operation, a replication operation, a continuousdata protection operation, a quota operation, a space managementoperation, or a space accounting operation.
 14. A data storage systemcomprising: a memory storing instructions; and a processorcommunicatively coupled to the memory and configured to execute theinstructions to: establish that an operation applied to a directoryhierarchy of a file system at a first time is to be selectivelyimplemented later in time; detect a request to modify a storage layerentity at a second time that is after the first time; and implement, inresponse to the request and based on a path set indicating that thestorage layer entity is associated with the directory hierarchy of thefile system at the first time, the operation on the storage layer entitybefore modifying the storage layer entity based on the request.
 15. Thedata storage system of claim 14, wherein the operation comprises asnapshot of the directory hierarchy.
 16. The data storage system ofclaim 14, wherein the storage layer entity comprises a block object thatimplements a file or directory of the directory hierarchy of the filesystem.
 17. The data storage system of claim 16, wherein the path setindicates any managed directory of the file system having a directorytree that includes the file or directory implemented by the blockobject.
 18. A method comprising: receiving a request to modify a storagelayer entity that implements a file service layer entity of a filesystem; determining, in response to the request and based on a path setindicating a relationship between the storage layer entity and adirectory of the file system, that there is a pending operation on thedirectory that is yet to be applied to the storage layer entity; andapplying, based on the determining, the pending action to the storagelayer entity before modifying the storage layer entity based on therequest.
 19. The method of claim 18, wherein the pending actioncomprises a snapshot of the directory.
 20. The method of claim 18,wherein the storage layer entity comprises a block object thatimplements a file or directory of a directory hierarchy of the directoryof the file system.